This document summarizes a computational fluid dynamics (CFD) simulation of flow around an Ahmed body, which is a simplified vehicle model used to study automotive aerodynamics. The simulation varied the rear slant angle of the Ahmed body from 0 to 40 degrees and analyzed the effects on drag and lift coefficients to determine the optimal angle for minimum drag. Pressure-based solver and k-Epsilon turbulence model were used in the simulation conducted in ANSYS Fluent. The study aimed to better understand drag and lift mechanisms and flow patterns like wake regions behind the vehicle body.
This document discusses computational fluid dynamics (CFD) analysis and optimization of geometric modifications to the Ahmed body to reduce drag and lift coefficients. The Ahmed body is a simplified bluff body shape used to model important car-like geometry features. The study aims to investigate how modifying parameters like rear slant angle, boat tail angle, and ramp angle can influence aerodynamic performance. CFD simulations are conducted using various turbulence models to analyze velocity contours and pressure distributions around modified geometries. The document reviews several past studies exploring techniques like rear slant angle manipulation, surface roughness elements, trailing edge blowing slots, boat tail configurations, and base bleed outlets for reducing drag on bluff bodies.
This document summarizes a study that uses computational fluid dynamics (CFD) simulations to investigate ways to reduce aerodynamic drag and increase stability of the Land Rover Discovery vehicle. The study validates CFD simulations of the baseline vehicle model against experimental data. It then analyzes modifications like adding a longitudinal ventilation duct or ditch on the roof to reduce drag. Simulations were run at various velocities and mesh refinements to optimize the analysis. Results show modifications can lower drag compared to the baseline model.
Computational Aerodynamics Research and Vehicle Engineering Development (CAR-...inventionjournals
Many Persons, both from industry and also private individuals have performed research in regards to this new issue. Many have performed research on aerodynamics on certain portions of the vehicle and also on effects of shape of the body and other technologies used such as Computational Fluid Dynamics and Wind tunnel Testing.The effects of these studies is seen in the industry today. Not so long ago,the vehicles were having shapes lose to boxes and today beautiful curves dominate the vehicles bodies. These curves not only help in the beauty of the vehicle but also help the vehicle in terms of aerodynamics and fuel efficiency. In this paper we would like to highlight some important topics related with aerodynamics and how they affect the drag of the vehicles. We shall also discuss on methods used in the industry today to calculate the aerodynamic efficiency of the vehicles and their effects.
International Journal of Computational Engineering Research(IJCER)ijceronline
This document summarizes research on the crosswind sensitivity of passenger cars and the influence of vehicle chassis characteristics. Experimental crosswind testing was conducted on seven vehicle configurations with seven drivers. A crosswind "gauntlet" test procedure exposed drivers to alternating crosswinds over 350 feet, eliciting stronger impressions than clustered wind pulses. Driver preferences linked certain chassis properties like weight distribution and suspension characteristics to lower measured responses. The research recommends a two-stage design process using static turning analyses and dynamic simulations to predict crosswind sensitivity.
- The document discusses external aerodynamic analysis of heavy commercial vehicles (HCVs) using computational fluid dynamics (CFD) simulation and wind tunnel testing.
- It aims to study the coefficient of drag of HCVs with different shapes and heights of wind deflectors. Three-dimensional models of the HCV are created in CATIA and analyzed in ANSYS-CFX to compare flow patterns and drag forces.
- The simulation results will be validated through subsonic wind tunnel testing of scaled physical models, which will also utilize smoke flow visualization and surface pressure distribution measurements.
Fluid-Structure Interaction Over an Aircraft WingIJERDJOURNAL
ABSTRACT:- Aircraft is a brilliant man-made structure which helps us to fly over the world. At the same time, aircraft is a complex structure to be checked and maintained for the aero elasticity due to aerodynamic properties. In this paper, the fluid-structure interaction problem in super critical NASA SC(2)-0412 airfoil is discussed. The main aim of this project is to find the best performance and deformation limit of the wing on different Mach numbers. This project is completely done by numerical methods of designing the wing using CATIA and flow properties in Computational Fluid Dynamics (CFD) method. Finally, the structural analysis for deformation is analysed in ANSYS. The analytical approach of fluid-structure interaction over an Aircraft wing is complex.
Assessment of Flow Control using Passive Devices around Bluff BodiesAnuragSingh1049
This article presents a review study on the experimental investigation of aerodynamic force on a car like bluff bodies along with the simulations using different turbulence models used in CFD (Computational Fluid Dynamics). The aim of the study is to find a useful method for the better design of a car body. It was observed that combination of wind tunnel experiments and CFD computation can lead to better aerodynamic design. Significant reduction in coefficient of the lift and drag for a car model were found when a more streamlined body design was adopted. Appropriate change in the slant angle for the car body can significantly reduce the fuel consumption. Also, the use of simulations in combination with the experimental observations helps in predicting the flow behavior more accurately.
IRJET- Experimentally and CFD Analysis on Spoiler in Wind Tunnel ExperimentIRJET Journal
1. Researchers experimentally tested a fabricated spoiler in a wind tunnel at different wind velocities and analyzed the results using computational fluid dynamics (CFD) software.
2. Both the wind tunnel experiments and CFD analysis yielded similar results for lift and drag coefficients, with a small percentage error between the two methods.
3. While CFD simulations are cheaper and easier than physical experiments, wind tunnel tests are still needed to validate CFD results, especially for turbulent flows.
This document discusses computational fluid dynamics (CFD) analysis and optimization of geometric modifications to the Ahmed body to reduce drag and lift coefficients. The Ahmed body is a simplified bluff body shape used to model important car-like geometry features. The study aims to investigate how modifying parameters like rear slant angle, boat tail angle, and ramp angle can influence aerodynamic performance. CFD simulations are conducted using various turbulence models to analyze velocity contours and pressure distributions around modified geometries. The document reviews several past studies exploring techniques like rear slant angle manipulation, surface roughness elements, trailing edge blowing slots, boat tail configurations, and base bleed outlets for reducing drag on bluff bodies.
This document summarizes a study that uses computational fluid dynamics (CFD) simulations to investigate ways to reduce aerodynamic drag and increase stability of the Land Rover Discovery vehicle. The study validates CFD simulations of the baseline vehicle model against experimental data. It then analyzes modifications like adding a longitudinal ventilation duct or ditch on the roof to reduce drag. Simulations were run at various velocities and mesh refinements to optimize the analysis. Results show modifications can lower drag compared to the baseline model.
Computational Aerodynamics Research and Vehicle Engineering Development (CAR-...inventionjournals
Many Persons, both from industry and also private individuals have performed research in regards to this new issue. Many have performed research on aerodynamics on certain portions of the vehicle and also on effects of shape of the body and other technologies used such as Computational Fluid Dynamics and Wind tunnel Testing.The effects of these studies is seen in the industry today. Not so long ago,the vehicles were having shapes lose to boxes and today beautiful curves dominate the vehicles bodies. These curves not only help in the beauty of the vehicle but also help the vehicle in terms of aerodynamics and fuel efficiency. In this paper we would like to highlight some important topics related with aerodynamics and how they affect the drag of the vehicles. We shall also discuss on methods used in the industry today to calculate the aerodynamic efficiency of the vehicles and their effects.
International Journal of Computational Engineering Research(IJCER)ijceronline
This document summarizes research on the crosswind sensitivity of passenger cars and the influence of vehicle chassis characteristics. Experimental crosswind testing was conducted on seven vehicle configurations with seven drivers. A crosswind "gauntlet" test procedure exposed drivers to alternating crosswinds over 350 feet, eliciting stronger impressions than clustered wind pulses. Driver preferences linked certain chassis properties like weight distribution and suspension characteristics to lower measured responses. The research recommends a two-stage design process using static turning analyses and dynamic simulations to predict crosswind sensitivity.
- The document discusses external aerodynamic analysis of heavy commercial vehicles (HCVs) using computational fluid dynamics (CFD) simulation and wind tunnel testing.
- It aims to study the coefficient of drag of HCVs with different shapes and heights of wind deflectors. Three-dimensional models of the HCV are created in CATIA and analyzed in ANSYS-CFX to compare flow patterns and drag forces.
- The simulation results will be validated through subsonic wind tunnel testing of scaled physical models, which will also utilize smoke flow visualization and surface pressure distribution measurements.
Fluid-Structure Interaction Over an Aircraft WingIJERDJOURNAL
ABSTRACT:- Aircraft is a brilliant man-made structure which helps us to fly over the world. At the same time, aircraft is a complex structure to be checked and maintained for the aero elasticity due to aerodynamic properties. In this paper, the fluid-structure interaction problem in super critical NASA SC(2)-0412 airfoil is discussed. The main aim of this project is to find the best performance and deformation limit of the wing on different Mach numbers. This project is completely done by numerical methods of designing the wing using CATIA and flow properties in Computational Fluid Dynamics (CFD) method. Finally, the structural analysis for deformation is analysed in ANSYS. The analytical approach of fluid-structure interaction over an Aircraft wing is complex.
Assessment of Flow Control using Passive Devices around Bluff BodiesAnuragSingh1049
This article presents a review study on the experimental investigation of aerodynamic force on a car like bluff bodies along with the simulations using different turbulence models used in CFD (Computational Fluid Dynamics). The aim of the study is to find a useful method for the better design of a car body. It was observed that combination of wind tunnel experiments and CFD computation can lead to better aerodynamic design. Significant reduction in coefficient of the lift and drag for a car model were found when a more streamlined body design was adopted. Appropriate change in the slant angle for the car body can significantly reduce the fuel consumption. Also, the use of simulations in combination with the experimental observations helps in predicting the flow behavior more accurately.
IRJET- Experimentally and CFD Analysis on Spoiler in Wind Tunnel ExperimentIRJET Journal
1. Researchers experimentally tested a fabricated spoiler in a wind tunnel at different wind velocities and analyzed the results using computational fluid dynamics (CFD) software.
2. Both the wind tunnel experiments and CFD analysis yielded similar results for lift and drag coefficients, with a small percentage error between the two methods.
3. While CFD simulations are cheaper and easier than physical experiments, wind tunnel tests are still needed to validate CFD results, especially for turbulent flows.
Aerodynamic Study about an Automotive Vehicle with Capacity for Only One Occu...IJERA Editor
The presented study describes the aerodynamic behavior of a compact, single occupant, automotive vehicle. To
optimize the aerodynamic characteristics of this vehicle, a flow dynamics study was conducted using a virtual
model. The outer surfaces of the vehicle body were designed using Computer Aided Design (CAD) tools and its
aerodynamic performance simulated virtually using Computational Fluid Dynamics (CFD) software. Parameters
such as pressure coefficient (Cp), coefficient of friction (Cf) and graphical analysis of the streamlines were used
to understand the flow dynamics and propose recommendations aimed at improving the coefficient of drag (Cd).
The identification of interaction points between the fluid and the flow structure was the primary focus of study to
develop these propositions. The study of phenomena linked to the characteristics of the model presented here,
allowed the identification of design features that should be avoided to generate improved aerodynamic
performance.
Strategies for Aerodynamic Development discusses computational techniques for aerodynamic shape optimization to reduce drag. Adjoint methods efficiently compute gradients with respect to design variables, allowing optimization of hundreds or thousands of variables at once. Free-form deformation uses control points to parameterize geometry changes, making complex geometry manipulation easier. Direct optimization of the Common Research Model wing minimized drag subject to constraints.
Cfd analysis of car body aerodynamics including effect of passive flow device...eSAT Journals
Abstract With the emphasis lying on increasing fuel efficiency of vehicles in order to combat rising fuel prices and environmental
challenges the manufacturers are thinking beyond the conventional vehicle systems by focusing on its aerodynamics. Aerodynamic
drag exceeds 50 per cent of the total resistance to motion at speeds above 70km/hr, and above 100 km/hr it is the most important
factor. The review is done to identify the various shortcomings of the automotive designers when it is in regards to flow
separation of air at the rear of the vehicle which causes most of the losses. This paper focuses on the work already done in the
field of aerodynamics starting with Ahmed Body. It is a bluff body with adjustable rear slant angle and the basis upon which the
aerodynamicists test their models. And then, moving onto passive aerodynamic enhancements for automobiles like vortex
generators and diffusers whose various dimensional modulations were discussed with several steps leading to its advancement in
vehicle body design. This brings to the simulation, Computational Fluid Dynamics (CFD) and its role in this analysis was
covered. CFD has been modified a lot from the beginning to increase the accuracy of its predictions. So the paper lists various
simulation techniques studied by the previous researchers in order to understand the wake region behind the car which has been
notoriously difficult to predict till date. Several aspects of aerodynamic drag that need further analysis to improve the
aerodynamic were highlighted.
Keywords: Drag Force, Drag Coefficient, Ahmed Body, CFD Simulation, Vehicle Aerodynamics, Passive Flow
Devices
CFD Simulation for Flow over Passenger Car Using Tail Plates for Aerodynamic ...IOSR Journals
This work proposes an effective numerical model based on the Computational Fluid Dynamics
(CFD) approach to obtain the flow structure around a passenger car with Tail Plates. The experimental work of
the test vehicle and grid system is constructed by ANSYS-14.0. FLUENT which is the CFD solver & employed in
the present work. In this study, numerical iterations are completed, then after aerodynamic data and detailed
complicated flow structure are visualized.
In the present work, model of generic passenger car has been developed in solid works-10 and
generated the wind tunnel and applied the boundary conditions in ANSYS workbench 14.0 platform then after
testing and simulation has been performed for the evaluation of drag coefficient for passenger car. In another
case, the aerodynamics of the most suitable design of tail plate is introduced and analysedfor the evaluation of
drag coefficient for passenger car. The addition of tail plates results in a reduction of the drag-coefficient
3.87% and lift coefficient 16.62% in head-on wind. Rounding the edges partially reduces drag in head-on wind
but does not bring about the significant improvements in the aerodynamic efficiency of the passenger car with
tail plates, it can be obtained. Hence, the drag force can be reduced by using add on devices on vehicle and fuel
economy, stability of a passenger car can be improved.
SIMULTANEOUS OPTIMIZATION OF SEMIACTIVE QUARTER CAR SUSPENSION PARAMETERS USI...ijmech
In present paper, a methodology is presented related to the optimization of semi-active quarter car model
suspension parameters having three degrees of freedom, subjected to bump type of road excitation.
Influence of primary suspension stiffness, primary suspension damping, secondary suspension stiffness and
secondary suspension damping are studied on the passenger ride comfort, taking root mean square (RMS)
values of passenger seat displacement and settling time into account. Semi-active quarter car model
assembled with magneto-rheological (MR) shock absorber is selected for optimization of suspension
parameters using Taguchi method in combination with Grey relational analysis. Confirmatory results with
simulation run indicates that the optimized results of suspension parameters are helpful in achieving the
best ride comfort to travelling passengers in terms of minimization of passenger seat displacement and
settling time values.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document discusses high speed tilting train technology. It provides background on tilting trains, which tilt the passenger cars inward on curves to reduce lateral acceleration and allow higher speeds on regular tracks. There are two main types of tilting systems - active systems which use sensors and actuators to control tilting, and passive systems which rely on centrifugal force and the tilt axis being above the center of gravity. The document examines the mechanics of tilting, comparing lateral acceleration in the track and car body. It also describes the typical components of tilting train mechanisms, including long-stroke air springs on the bogies and hydraulic actuators to control tilting.
Drag Reduction of Front Wing of an F1 Car using Adjoint Optimisationyasirmaliq
The Project Poster summarizes the aims and objectives of the Final Year Dissertation. The project starts with a detailed study on the parameters that tend to affect the performance of front wings of an F1 car and goes through designing the front wings(3) with endplates and wheel, meshing it, solving/analysing the flow and finally optimising the selected geometry using Fluent Adjoint Solver for efficient performance.
Adjoint optimisation technique is used to achieve optimal performance from the front wings. It's the most successful shape optimisation method as it's independent of the number of design variables exponentially reducing computational time and cost. The emphasis has been put on optimising the shape of the front wings using the Adjoint method as it’s the most efficient and computationally inexpensive method for design optimisation. The approach towards shape optimisation is downforce constrained drag minimization as it would result in keeping a constraint on downforce and reducing the drag at the same time, thus producing optima for a given downforce/drag value.
This document discusses how aerodynamics can improve vehicle performance in various racing events by increasing downforce. Downforce pushes the tires into the road, allowing for increased cornering ability without a significant weight penalty. Analysis of the skid pad, slalom, and acceleration events shows that a car with an aerodynamic package could achieve faster lap times by producing higher lateral and transient lateral forces. While drag also increases with downforce, the calculations show the engine power is sufficient to overcome these forces for the speeds in these events. Therefore, an aerodynamic package has the potential to significantly improve performance.
The document discusses the aerodynamics of ground vehicles. It presents data on the pressure coefficients on a vehicle with and without a fairing from wind tunnel tests at speeds of 10m/s and 20m/s. The addition of a fairing reduced pressure drag by delaying flow separation and decreasing pressure differences on the vehicle surface. Flow separation occurs more easily on bluff bodies and causes higher drag due to larger eddy formation compared to streamlined shapes. Fairings help streamline the flow and decrease drag forces substantially, improving fuel efficiency for heavy vehicles.
IRJET-Subsonic Flow Study and Analysis on Rotating Cylinder AirfoilIRJET Journal
This document presents a study on modifying the lift characteristics of a conventional symmetrical airfoil (NACA 0012) by adding a rotating cylinder. A numerical analysis and computational fluid dynamics simulation were conducted. Two cases were considered: a cylinder with 13mm diameter located at the 0.125 chord point, and a 15mm cylinder at the 0.25 chord point. The presence of a rotating cylinder was found to significantly increase the airfoil's lift at zero angle of attack through momentum injection, by up to 100%. It also delayed stall characteristics. The document outlines the methodology, including the airfoil geometry, range of air velocities and cylinder rotation speeds studied, and equations used to model static and total pressure.
Analysis Of NACA 6412 Airfoil (Purpose: Propeller For Flying Bike)IOSR Journals
This document analyzes the NACA 6412 airfoil for use as a propeller on a flying bike. It summarizes the analysis conducted using JavaProp software. The analysis found that a two-blade propeller with the NACA 6412 airfoil produced a thrust of 155.84N, meeting the target thrust needed. When the propeller was modeled with a shroud, thrust increased to 179.39N. Maximum thrust of 179.41N was produced when using a shroud and square blade tips. The two-blade propeller was determined to be preferable to a three-blade design due to lower weight, while still producing the necessary thrust.
This document outlines the aerodynamic design process for a Formula Student race car. It discusses theory, conceptual wing designs, theoretical lift calculations, and experimental testing. The goal is to prove the benefits of front and rear wings for improving stability, braking, and cornering at low speeds. The design process involves baseline testing, flow visualization, selecting airfoil profiles, sizing wings, and conducting coast down and wind tunnel tests to evaluate downforce. Computational fluid dynamics simulations are also used to analyze pressure and velocity contours. The results will help determine the most effective wing designs for the low speeds of the Formula Student car.
Car Dynamics using Quarter Model and Passive Suspension, Part II: A Novel Sim...IOSR Journals
This document presents research on using a quarter-car model and passive suspension to analyze the dynamics of a vehicle crossing a novel simple harmonic speed hump. The study uses MATLAB simulation of a quarter-car model to investigate the effect of hump dimensions and vehicle speed on ride comfort. It is found that a simple harmonic hump of 9m length allows vehicle speeds up to 30 km/h while maintaining ride comfort. A diagram is presented showing maximum vehicle speed for different hump dimensions that meet ride comfort standards.
Design of Rear wing for high performance cars and Simulation using Computatio...IJTET Journal
The performance of a sports car is not only limited to its engine power but also to aerodynamic properties of the car. By decreasing the drag force it is possible to reduce the engine power required to achieve same top speed thus decreasing the fuel requirement. The stability of a sports car is considerably important at high speed. The provision of a rear wing increases the downforce thus reducing the rear axle lift and provides increased traction. In this study an optimum rear wing is designed for the high performance car so as to decrease drag and increase downforce. The CAD designed baseline model with or without rear wing is being analyzed in computational fluid dynamics software. The lift and drag coefficient are calculated for all the design thus an optimum rear wing is designed for the considered baseline model.
Investigation of slipstreaming effect between a semi trailer truck and a seda...Researchshare4200
The study focuses on the slipstreaming effect on an aerodynamic sedan vehicle, trailing a semi-trailer truck on highways. A Subsonic wind tunnel (100×100×100 cm) is used to investigate the effect of slipstreaming. For design purpose, solid works software is used. Wooden models of semi-trailer truck and a sedan car have been constructed. In this experiment, the effect of distance of separation of the vehicles to slipstreaming has been studied and the critical distance is identified. The relative drag during slipstreaming at different velocities of the critical distance has also been addressed. From this investigation it has been observed that slipstreaming is effective at higher velocities of the vehicles under consideration.
IRJET- Fluid Dynamics Simulation of a Car Spoiler for Drag Reduction and to I...IRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) software to simulate different car spoiler designs. The goal was to reduce aerodynamic drag and increase downforce. Various NACA airfoil profiles were tested at different angles of attack to select the most efficient design. Spoiler heights were also varied to determine the optimal dimension. The CFD simulations were then used to analyze pressure and velocity distributions for the different spoiler configurations. The most effective design minimized low pressure areas on the top surface while maximizing under-spoiler vacuum to increase downforce without excessive drag.
Research Proposal for Turbulence Examination of Class-8 VehiclesSalman Rahmani
This proposal outlines a study to reduce drag on Class-8 vehicles through the use of cylindrical modifications to the trailer. The researcher will computationally simulate and analyze two designs: 1) dual rotating cylinders mounted vertically along the trailing edge with a plate between, and 2) four rotating cylinders (two vertical, two horizontal) along the trailing edge with a plate. Simulations of each design will be run at various rotational speeds (alphas) to analyze the effects on drag. The goal is to gain insights into fluid dynamics around large objects to help reduce pollution from transportation vehicles. The timeline spans from September 2016 to May 2017 for modeling, simulations, data analysis and reporting.
Performance Study of Wind Friction Reduction Attachments for Van Using Comput...IJERA Editor
This document summarizes a study that used computational fluid dynamics (CFD) to analyze the impact of different wind friction reduction attachments on the aerodynamic drag of a van. Six attachment models were designed and their coefficients of drag were calculated and compared to a baseline van without attachments. Model E, with front and truncated rear attachments, performed best with a coefficient of drag of 0.230, a 46% reduction from the baseline van. Analytical calculations estimated the potential fuel economy improvements from the reduced drag, with Model E achieving a mileage increase of up to 38% compared to the baseline van. The results suggest attaching aerodynamic devices can significantly improve the efficiency of commercial vehicles.
The document discusses techniques for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It proposes two new methods: 1) shifting two null subcarriers among two data subcarriers and 2) switching null subcarriers with data subcarriers. Through MATLAB simulations, the proposed methods achieve around 1.4dB lower PAPR compared to existing methods, with the shifting null subcarriers method performing best. The bit error rate performance of the proposed shifting method is also better than existing approaches.
Dynamic Programming approach in Two Echelon Inventory System with Repairable ...IOSR Journals
This document presents a two-echelon inventory system model with repairable items. The system consists of operating sites (base stations) and a depot. Each base station has inventory to fulfill failed item demands and is replenished from the depot. Failed items arrive at base stations according to a Poisson process and are inspected. Inspection times are exponential. Inspected items are either repaired at the depot or condemned. The system aims to determine optimal ordering policies to minimize average costs using Markov decision processes and dynamic programming. Numerical examples are provided to illustrate the model.
Aerodynamic Study about an Automotive Vehicle with Capacity for Only One Occu...IJERA Editor
The presented study describes the aerodynamic behavior of a compact, single occupant, automotive vehicle. To
optimize the aerodynamic characteristics of this vehicle, a flow dynamics study was conducted using a virtual
model. The outer surfaces of the vehicle body were designed using Computer Aided Design (CAD) tools and its
aerodynamic performance simulated virtually using Computational Fluid Dynamics (CFD) software. Parameters
such as pressure coefficient (Cp), coefficient of friction (Cf) and graphical analysis of the streamlines were used
to understand the flow dynamics and propose recommendations aimed at improving the coefficient of drag (Cd).
The identification of interaction points between the fluid and the flow structure was the primary focus of study to
develop these propositions. The study of phenomena linked to the characteristics of the model presented here,
allowed the identification of design features that should be avoided to generate improved aerodynamic
performance.
Strategies for Aerodynamic Development discusses computational techniques for aerodynamic shape optimization to reduce drag. Adjoint methods efficiently compute gradients with respect to design variables, allowing optimization of hundreds or thousands of variables at once. Free-form deformation uses control points to parameterize geometry changes, making complex geometry manipulation easier. Direct optimization of the Common Research Model wing minimized drag subject to constraints.
Cfd analysis of car body aerodynamics including effect of passive flow device...eSAT Journals
Abstract With the emphasis lying on increasing fuel efficiency of vehicles in order to combat rising fuel prices and environmental
challenges the manufacturers are thinking beyond the conventional vehicle systems by focusing on its aerodynamics. Aerodynamic
drag exceeds 50 per cent of the total resistance to motion at speeds above 70km/hr, and above 100 km/hr it is the most important
factor. The review is done to identify the various shortcomings of the automotive designers when it is in regards to flow
separation of air at the rear of the vehicle which causes most of the losses. This paper focuses on the work already done in the
field of aerodynamics starting with Ahmed Body. It is a bluff body with adjustable rear slant angle and the basis upon which the
aerodynamicists test their models. And then, moving onto passive aerodynamic enhancements for automobiles like vortex
generators and diffusers whose various dimensional modulations were discussed with several steps leading to its advancement in
vehicle body design. This brings to the simulation, Computational Fluid Dynamics (CFD) and its role in this analysis was
covered. CFD has been modified a lot from the beginning to increase the accuracy of its predictions. So the paper lists various
simulation techniques studied by the previous researchers in order to understand the wake region behind the car which has been
notoriously difficult to predict till date. Several aspects of aerodynamic drag that need further analysis to improve the
aerodynamic were highlighted.
Keywords: Drag Force, Drag Coefficient, Ahmed Body, CFD Simulation, Vehicle Aerodynamics, Passive Flow
Devices
CFD Simulation for Flow over Passenger Car Using Tail Plates for Aerodynamic ...IOSR Journals
This work proposes an effective numerical model based on the Computational Fluid Dynamics
(CFD) approach to obtain the flow structure around a passenger car with Tail Plates. The experimental work of
the test vehicle and grid system is constructed by ANSYS-14.0. FLUENT which is the CFD solver & employed in
the present work. In this study, numerical iterations are completed, then after aerodynamic data and detailed
complicated flow structure are visualized.
In the present work, model of generic passenger car has been developed in solid works-10 and
generated the wind tunnel and applied the boundary conditions in ANSYS workbench 14.0 platform then after
testing and simulation has been performed for the evaluation of drag coefficient for passenger car. In another
case, the aerodynamics of the most suitable design of tail plate is introduced and analysedfor the evaluation of
drag coefficient for passenger car. The addition of tail plates results in a reduction of the drag-coefficient
3.87% and lift coefficient 16.62% in head-on wind. Rounding the edges partially reduces drag in head-on wind
but does not bring about the significant improvements in the aerodynamic efficiency of the passenger car with
tail plates, it can be obtained. Hence, the drag force can be reduced by using add on devices on vehicle and fuel
economy, stability of a passenger car can be improved.
SIMULTANEOUS OPTIMIZATION OF SEMIACTIVE QUARTER CAR SUSPENSION PARAMETERS USI...ijmech
In present paper, a methodology is presented related to the optimization of semi-active quarter car model
suspension parameters having three degrees of freedom, subjected to bump type of road excitation.
Influence of primary suspension stiffness, primary suspension damping, secondary suspension stiffness and
secondary suspension damping are studied on the passenger ride comfort, taking root mean square (RMS)
values of passenger seat displacement and settling time into account. Semi-active quarter car model
assembled with magneto-rheological (MR) shock absorber is selected for optimization of suspension
parameters using Taguchi method in combination with Grey relational analysis. Confirmatory results with
simulation run indicates that the optimized results of suspension parameters are helpful in achieving the
best ride comfort to travelling passengers in terms of minimization of passenger seat displacement and
settling time values.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document discusses high speed tilting train technology. It provides background on tilting trains, which tilt the passenger cars inward on curves to reduce lateral acceleration and allow higher speeds on regular tracks. There are two main types of tilting systems - active systems which use sensors and actuators to control tilting, and passive systems which rely on centrifugal force and the tilt axis being above the center of gravity. The document examines the mechanics of tilting, comparing lateral acceleration in the track and car body. It also describes the typical components of tilting train mechanisms, including long-stroke air springs on the bogies and hydraulic actuators to control tilting.
Drag Reduction of Front Wing of an F1 Car using Adjoint Optimisationyasirmaliq
The Project Poster summarizes the aims and objectives of the Final Year Dissertation. The project starts with a detailed study on the parameters that tend to affect the performance of front wings of an F1 car and goes through designing the front wings(3) with endplates and wheel, meshing it, solving/analysing the flow and finally optimising the selected geometry using Fluent Adjoint Solver for efficient performance.
Adjoint optimisation technique is used to achieve optimal performance from the front wings. It's the most successful shape optimisation method as it's independent of the number of design variables exponentially reducing computational time and cost. The emphasis has been put on optimising the shape of the front wings using the Adjoint method as it’s the most efficient and computationally inexpensive method for design optimisation. The approach towards shape optimisation is downforce constrained drag minimization as it would result in keeping a constraint on downforce and reducing the drag at the same time, thus producing optima for a given downforce/drag value.
This document discusses how aerodynamics can improve vehicle performance in various racing events by increasing downforce. Downforce pushes the tires into the road, allowing for increased cornering ability without a significant weight penalty. Analysis of the skid pad, slalom, and acceleration events shows that a car with an aerodynamic package could achieve faster lap times by producing higher lateral and transient lateral forces. While drag also increases with downforce, the calculations show the engine power is sufficient to overcome these forces for the speeds in these events. Therefore, an aerodynamic package has the potential to significantly improve performance.
The document discusses the aerodynamics of ground vehicles. It presents data on the pressure coefficients on a vehicle with and without a fairing from wind tunnel tests at speeds of 10m/s and 20m/s. The addition of a fairing reduced pressure drag by delaying flow separation and decreasing pressure differences on the vehicle surface. Flow separation occurs more easily on bluff bodies and causes higher drag due to larger eddy formation compared to streamlined shapes. Fairings help streamline the flow and decrease drag forces substantially, improving fuel efficiency for heavy vehicles.
IRJET-Subsonic Flow Study and Analysis on Rotating Cylinder AirfoilIRJET Journal
This document presents a study on modifying the lift characteristics of a conventional symmetrical airfoil (NACA 0012) by adding a rotating cylinder. A numerical analysis and computational fluid dynamics simulation were conducted. Two cases were considered: a cylinder with 13mm diameter located at the 0.125 chord point, and a 15mm cylinder at the 0.25 chord point. The presence of a rotating cylinder was found to significantly increase the airfoil's lift at zero angle of attack through momentum injection, by up to 100%. It also delayed stall characteristics. The document outlines the methodology, including the airfoil geometry, range of air velocities and cylinder rotation speeds studied, and equations used to model static and total pressure.
Analysis Of NACA 6412 Airfoil (Purpose: Propeller For Flying Bike)IOSR Journals
This document analyzes the NACA 6412 airfoil for use as a propeller on a flying bike. It summarizes the analysis conducted using JavaProp software. The analysis found that a two-blade propeller with the NACA 6412 airfoil produced a thrust of 155.84N, meeting the target thrust needed. When the propeller was modeled with a shroud, thrust increased to 179.39N. Maximum thrust of 179.41N was produced when using a shroud and square blade tips. The two-blade propeller was determined to be preferable to a three-blade design due to lower weight, while still producing the necessary thrust.
This document outlines the aerodynamic design process for a Formula Student race car. It discusses theory, conceptual wing designs, theoretical lift calculations, and experimental testing. The goal is to prove the benefits of front and rear wings for improving stability, braking, and cornering at low speeds. The design process involves baseline testing, flow visualization, selecting airfoil profiles, sizing wings, and conducting coast down and wind tunnel tests to evaluate downforce. Computational fluid dynamics simulations are also used to analyze pressure and velocity contours. The results will help determine the most effective wing designs for the low speeds of the Formula Student car.
Car Dynamics using Quarter Model and Passive Suspension, Part II: A Novel Sim...IOSR Journals
This document presents research on using a quarter-car model and passive suspension to analyze the dynamics of a vehicle crossing a novel simple harmonic speed hump. The study uses MATLAB simulation of a quarter-car model to investigate the effect of hump dimensions and vehicle speed on ride comfort. It is found that a simple harmonic hump of 9m length allows vehicle speeds up to 30 km/h while maintaining ride comfort. A diagram is presented showing maximum vehicle speed for different hump dimensions that meet ride comfort standards.
Design of Rear wing for high performance cars and Simulation using Computatio...IJTET Journal
The performance of a sports car is not only limited to its engine power but also to aerodynamic properties of the car. By decreasing the drag force it is possible to reduce the engine power required to achieve same top speed thus decreasing the fuel requirement. The stability of a sports car is considerably important at high speed. The provision of a rear wing increases the downforce thus reducing the rear axle lift and provides increased traction. In this study an optimum rear wing is designed for the high performance car so as to decrease drag and increase downforce. The CAD designed baseline model with or without rear wing is being analyzed in computational fluid dynamics software. The lift and drag coefficient are calculated for all the design thus an optimum rear wing is designed for the considered baseline model.
Investigation of slipstreaming effect between a semi trailer truck and a seda...Researchshare4200
The study focuses on the slipstreaming effect on an aerodynamic sedan vehicle, trailing a semi-trailer truck on highways. A Subsonic wind tunnel (100×100×100 cm) is used to investigate the effect of slipstreaming. For design purpose, solid works software is used. Wooden models of semi-trailer truck and a sedan car have been constructed. In this experiment, the effect of distance of separation of the vehicles to slipstreaming has been studied and the critical distance is identified. The relative drag during slipstreaming at different velocities of the critical distance has also been addressed. From this investigation it has been observed that slipstreaming is effective at higher velocities of the vehicles under consideration.
IRJET- Fluid Dynamics Simulation of a Car Spoiler for Drag Reduction and to I...IRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) software to simulate different car spoiler designs. The goal was to reduce aerodynamic drag and increase downforce. Various NACA airfoil profiles were tested at different angles of attack to select the most efficient design. Spoiler heights were also varied to determine the optimal dimension. The CFD simulations were then used to analyze pressure and velocity distributions for the different spoiler configurations. The most effective design minimized low pressure areas on the top surface while maximizing under-spoiler vacuum to increase downforce without excessive drag.
Research Proposal for Turbulence Examination of Class-8 VehiclesSalman Rahmani
This proposal outlines a study to reduce drag on Class-8 vehicles through the use of cylindrical modifications to the trailer. The researcher will computationally simulate and analyze two designs: 1) dual rotating cylinders mounted vertically along the trailing edge with a plate between, and 2) four rotating cylinders (two vertical, two horizontal) along the trailing edge with a plate. Simulations of each design will be run at various rotational speeds (alphas) to analyze the effects on drag. The goal is to gain insights into fluid dynamics around large objects to help reduce pollution from transportation vehicles. The timeline spans from September 2016 to May 2017 for modeling, simulations, data analysis and reporting.
Performance Study of Wind Friction Reduction Attachments for Van Using Comput...IJERA Editor
This document summarizes a study that used computational fluid dynamics (CFD) to analyze the impact of different wind friction reduction attachments on the aerodynamic drag of a van. Six attachment models were designed and their coefficients of drag were calculated and compared to a baseline van without attachments. Model E, with front and truncated rear attachments, performed best with a coefficient of drag of 0.230, a 46% reduction from the baseline van. Analytical calculations estimated the potential fuel economy improvements from the reduced drag, with Model E achieving a mileage increase of up to 38% compared to the baseline van. The results suggest attaching aerodynamic devices can significantly improve the efficiency of commercial vehicles.
The document discusses techniques for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It proposes two new methods: 1) shifting two null subcarriers among two data subcarriers and 2) switching null subcarriers with data subcarriers. Through MATLAB simulations, the proposed methods achieve around 1.4dB lower PAPR compared to existing methods, with the shifting null subcarriers method performing best. The bit error rate performance of the proposed shifting method is also better than existing approaches.
Dynamic Programming approach in Two Echelon Inventory System with Repairable ...IOSR Journals
This document presents a two-echelon inventory system model with repairable items. The system consists of operating sites (base stations) and a depot. Each base station has inventory to fulfill failed item demands and is replenished from the depot. Failed items arrive at base stations according to a Poisson process and are inspected. Inspection times are exponential. Inspected items are either repaired at the depot or condemned. The system aims to determine optimal ordering policies to minimize average costs using Markov decision processes and dynamic programming. Numerical examples are provided to illustrate the model.
This document summarizes a research paper about power management and coordination control of a standalone photovoltaic (PV) system. It discusses two possible topological configurations for standalone PV systems - series and parallel connected. The parallel connected topology is determined to have advantages over the series connected topology by reducing power losses and hardware costs while maintaining efficiency. A state diagram is proposed to illustrate the concept of coordination control between the PV power source and load. Simulation results are presented that analyze the power flow and operational characteristics of a parallel connected PV system under different load conditions.
This document simulates a linear oscillating tubular motor (LOTM) using mathematical equations and computer tools. It begins by describing the components and operating principle of the LOTM, which consists of an iron bar moving inside a coil. The displacement of the iron bar causes periodic variations in the coil inductance.
The document then presents the mathematical equations that govern the LOTM's operation in terms of inductance as a function of displacement. A block diagram shows how these electrical and mechanical equations are solved using simulation. Graphical results from the simulation show how parameters like inductance, magnetic force, and speed vary over time and displacement. In conclusion, the document discusses how further optimization of the LOTM's magnetic circuit and
The document describes a study that used the Taguchi method to optimize engine parameters to reduce particulate matter (PM) and smoke opacity emissions from a diesel engine fueled with jatropha biodiesel blends. Three control factors were tested - engine load, percentage of biodiesel in the blend, and fuel injection pressure. Experiments were designed using an L16 orthogonal array. Results found that engine load had the greatest influence on emissions, followed by percentage of biodiesel, with injection pressure having the least effect. The optimized parameters were found to be an engine load of 25%, a biodiesel percentage of 40%, and an injection pressure of 220 bar.
This document compares the performance of three mobile ad hoc network (MANET) routing protocols: AODV, FSR, and IERP. It uses the QualNet network simulator to evaluate these protocols based on various metrics like throughput, average jitter, average end-to-end delay, and packet delivery ratio. The protocols are evaluated under different node speeds on a grid topology network with 90 nodes over an area of 1500x1500 meters. Simulation results show that AODV generally performs best in terms of throughput and packet delivery ratio across varying node speeds, while FSR performs worst for these metrics. IERP shows the worst performance for average end-to-end delay and average jitter as node speed increases.
This document reviews the design of an energy-optimized wireless sensor node that encrypts data for transmission. It discusses how sensing schemes that group nodes into clusters and transmit aggregated data can reduce energy consumption compared to individual node transmissions. The proposed node design calculates the minimum transmission power needed based on received signal strength and uses a periodic sleep/wake cycle to optimize energy when not sensing or transmitting. It aims to encrypt data at both the node and network level to further optimize energy usage for wireless communication.
This document provides an overview of contemporary security problems in wireless mesh networks. It discusses security vulnerabilities at different layers of the communication protocol stack for wireless mesh networks, including the physical, link, and network layers. At the physical layer, jamming attacks are a risk. The link layer is vulnerable to passive eavesdropping, spoofing, congestion attacks, and replay attacks. The network layer faces risks from routing attacks like black hole and gray hole attacks, as well as Sybil attacks. Overall, the document analyzes different types of attacks that threaten the security of wireless mesh networks.
This document analyzes the optimization of an air filter in an automobile diesel engine using computational fluid dynamics (CFD). It begins by describing the components and functions of an air intake system. It then discusses using CFD to simulate different designs of the air filter geometry. The study analyzed a standard air filter model and four designs with different baffle plate arrangements. CFD analysis found the pressure drop decreased across the designs, with the final design showing a 14.8% reduction in pressure drop compared to the standard model. In conclusion, CFD analysis enabled optimal design of the air filter system with reduced development time and costs.
This document summarizes research on the preparation and characterization of titanium-doped barium ferrite (BFTO) nanopowders. BFTO powders with compositions of BaFe(12-x)TixO19, where x=0.32 and x=0.36, were synthesized using a sol-gel method. The powders were characterized using XRD, SEM, and FTIR. XRD analysis confirmed the formation of a single tetragonal phase and particle sizes ranging from 15-50 nm. SEM images showed irregularly shaped plate-like particles 10-40 nm in size. FTIR spectra exhibited peaks corresponding to metal-oxygen bonds and residual organic groups from the synthesis method.
This document analyzes the effect of node density on different routing protocols under FTP and HTTP applications. It simulates scenarios with varying node densities (20-130 nodes) using routing protocols AODV, DSR, GRP and OLSR. Key quality of service (QoS) metrics - throughput, delay, network load and packet delivery ratio - are evaluated and compared. The results show that OLSR generally performs best in terms of throughput and delay for both FTP and HTTP applications. GRP performs best for network load, while AODV has the highest packet delivery ratio for FTP. In conclusion, OLSR is the best overall routing protocol for supporting FTP and HTTP applications in mobile ad-hoc networks according to
The document experimentally investigates friction stir welding of aluminum AA6061 alloy joints. Tests were conducted to determine the surface roughness, Rockwell hardness, and tensile strength of friction stir welded AA6061 alloy joints at different tool rotational speeds and feed rates. The results found that surface roughness, hardness, and tensile strength values were optimized at a tool speed of 950 rpm and feed rate of 16 mm/min, with surface roughness and hardness initially increasing and then decreasing with tool speed, and tensile strength continuously increasing with tool speed up to the optimal values.
This document summarizes a review of cooling tower performance and opportunities for energy savings through economizer operation. It discusses how cooling towers work and rejects heat to the atmosphere. It notes that cooling towers are a major energy user in buildings and manufacturing. The document then reviews the Merkel theory model for predicting cooling tower performance and its limitations, especially at low fan speeds and wet bulb temperatures. It proposes creating a new model to more accurately predict performance under these conditions to better assess energy savings opportunities like economizer operation.
This document presents a single phase to three phase matrix converter topology for electric traction drives. The matrix converter replaces the multiple conversion stages of a conventional AC-DC-AC converter with a single stage direct AC-AC conversion. The converter analysis is presented using a separation and link approach, which treats the converter as two equivalent circuits during the positive and negative periods of the AC source voltage. Sinusoidal pulse width modulation control is used to control the bi-directional switches in the converter in order to obtain the desired three phase output voltage and frequency for driving an induction traction motor. Simulation results indicate this matrix converter is a feasible replacement for the conversion stages in existing AC traction drive systems.
The document presents a mathematical modeling and analysis of the influence of process parameters on material removal rate (MRR) during electrical discharge machining (EDM) of stainless steel 304. Experiments were conducted to determine the effects of peak current, pulse on time, and pulse off time on MRR. Using Taguchi methods, an optimal combination of parameters was identified to achieve maximum MRR. Analysis of variance confirmed the significant effects of the parameters on MRR. Regression analysis was then used to develop a second order full quadratic mathematical model relating MRR to the process parameters. The model was found to have acceptable accuracy in predicting response values based on its R2 and adjusted R2 values. Interaction effects between the parameters were also studied.
This document summarizes an experimental study that investigated heat transfer enhancement in rectangular fin arrays with circular perforations. The researchers measured heat transfer and other parameters for solid and perforated fins under varying flow conditions. For the perforated fins, they found enhancement in heat transfer compared to solid fins. Specifically, they tested parallel and cross fins made of aluminum with dimensions of 100mm by 60mm by 5mm thickness. Testing was done with air flow velocities from 3000-6000 Reynolds number. Results showed the heat transfer coefficient was higher for cross fins (242.58 W/m2-K) than parallel fins (233.30 W/m2-K), indicating roughness created by the cross-cut pattern improved heat transfer over the single
This document analyzes the admittance characteristics of an H-plane tee junction formed by coupling two rectangular waveguides of different bands through an inclined slot in the narrow wall. The analysis uses concepts of self-reaction and discontinuity in modal current to determine the admittance loading, coupling, and voltage standing wave ratio as functions of slot width, length, and inclination angle. Results are compared to practical measurements. Previous work analyzing longitudinal and transverse slots is discussed, but no prior literature examines an inclined slot between waveguides of different bands.
This document summarizes a study on the physicochemical properties of soil affected by municipal solid waste (MSW) in a densely populated tropical region of Onitsha, Nigeria. Soil samples were collected from three locations - an uncontaminated control area 15 meters from two disposal sites, the crest formation at one site, and the basin formation at another. The samples were analyzed for properties like pH, organic matter, total nitrogen, heavy metals, and cation exchange capacity. Results showed increases in these parameters with depth. pH, nitrogen, zinc and iron were higher at the crest, while lead was higher at the basin. Aggregate stability decreased significantly at the basin compared to the control. Calculated values for tested parameters at
This document describes the design and optimization of a ground attack aircraft. It outlines the three phases of aircraft design: conceptual, preliminary, and detailed design. In the conceptual design phase, configurations like low wing, H-tail, and turbofan engines were selected. In preliminary design, parameters like maximum take-off weight, wing area, and engine thrust were estimated. The detailed design phase involves developing detailed designs for components like the wing, tail, fuselage, landing gear, and propulsion system. Design requirements are established and each component is optimized to meet the design goals.
This document analyzes irrigation distribution networks using demand-driven analysis (DDA) and pressure-driven analysis (PDA). It summarizes the key differences between the two approaches and the results of applying each to a case study network. DDA uses fixed demands regardless of pressure, while PDA accounts for how demand varies with pressure based on sprinkler characteristics. The document finds that PDA yields higher minimum pressures and less variation across demand groups. It also allows evaluating how demands are influenced by pressure changes. Overall, PDA provides a better representation of real network operation compared to DDA.
Performance Study of Wind Friction Reduction Attachments for Van Using Comput...IJERA Editor
Road transport is the key factor as it is the major method to connect places through land. Along with wide use of internal combustion engines for this purpose comes the massive consumption of fossil fuels by vehicles. Most of the research today is toward making efficient machines. This paper mainly deals with providing attachments to existing models of vehicle to make it more efficient. An assessment of the impact of aerodynamic drag and its relationship to energy consumption presented. A few models are designed and analysed for reducing drag with the help of Attachments. Solid works is used to model and ANSYS Fluent is used for CFD analysis. The results of Cd of various configuration is analysed, 0.427 being the Cd for conventional Van is reduced to 0.234 for van with front and rear attachment
Aero-acoustic investigation over a 3-dimensional open sunroof using CFDIRJET Journal
This document describes a computational fluid dynamics (CFD) study of buffeting noise from an open sunroof on a simplified 3D car model. The researchers will use the detached eddy simulation (DES) method in ANSYS Fluent to analyze pressure characteristics at different vehicle speeds. They will create a 3D virtual wind tunnel domain around the car model and assign appropriate boundary conditions. Pressure distributions obtained from simulations of closed and open sunroof cases will help establish an efficient design for a sunroof deflector to reduce buffeting noise.
This document summarizes an aerodynamic analysis of a car model conducted using computational fluid dynamics (CFD) software to reduce drag force. The original Swift Dzire car model and two modified models - a "fastback" design with a sloped rear and a model with a rear spoiler - were simulated at 144 km/hr. The original model had a drag coefficient of 0.375. The fastback design had a lower drag coefficient of 0.335 due to delayed flow separation at the rear. The spoiler model had an even lower drag coefficient of 0.35, as the inverted wing spoiler produced downward force to increase traction at high speeds. CFD analysis provided insight into pressure and velocity contours to understand
This document summarizes two computational studies of flow over an Ahmed body, a simplified car model. Case study 1 compares RANS and hybrid RANS-LES turbulence models in simulations of 25 and 35 degree rear slant angles. It finds that hybrid models overpredict drag coefficient compared to experiments. Case study 2 describes a grid-dependence study of three mesh sizes to accurately predict drag coefficient, finding the medium grid provides the best balance of accuracy and computational cost. The document concludes the Ahmed body is a useful benchmark for studying vehicle aerodynamics and quantifying drag, with rear slant angle being a major factor influencing overall drag coefficient.
Aerodynamic analysis and optimization of wind deflector in a Commercial load ...AM Publications
In the field of commercial goods transport, trucks have an important place. One of the main problems faced by truck manufacturers is the Air resistance associated with the highway running. Since trucks have a large frontal area and the presence of a trailer also leads to the truck experiencing significant resistance which has to be overcome. This can be reduced through the use of wind deflectors. A well-designed wind deflector can reduce wind resistance to a certain extent. Optimizing the angle of the wind deflector also causes reduced drag force acting on the vehicle, thereby reducing the fuel intake. Here the initial drag of 2050 N is reduced to 1688.453 N using a 1.75 m wind deflector at 45 degree angle resulting in the reduction of drag by 17.6%.
IRJET- Aerodynamic Analysis on a Car to Reduce Drag Force using Vertex GeneratorIRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) to analyze aerodynamic drag on a car model and evaluate methods for reducing drag through the addition of vortex generators. Seven different vertex generator designs were modeled and their effects on drag reduction were evaluated using CFD software. The goal was to improve fuel efficiency and vehicle performance by reducing aerodynamic drag through optimized vortex generator placement on the rear of the vehicle.
A Review on Drag Reduction Methods of Ahmed Body at Different Rear Slant Angl...IRJET Journal
This document reviews different methods for reducing drag on an Ahmed body vehicle model using computational fluid dynamics (CFD). It begins with background on aerodynamic drag and introduces the Ahmed body model. Several studies are summarized that used CFD to simulate adding devices like vortex generators, diffusers, flaps, and spoilers to Ahmed body models with different rear slant angles. These add-on devices were found to reduce drag by percentages ranging from 3-8% in most cases studied. The best devices and configurations resulted in drag reductions as high as 21-36%. CFD provides flow visualization to analyze how these devices alter wake flows and pressure distributions to reduce drag.
This document discusses drag force values for sedan vehicle profiles. It analyzes drag forces on different sedan dimensions and front end areas through computational fluid dynamics simulations. The simulations analyzed 72 sedan models with varying geometry and dimensions. The results showed designs with more airfoil-like shapes had lower drag forces and coefficients, between 0.135-0.186 N. However, these designs may not optimize pedestrian safety. The best designs balanced low drag with acceptable head injury criteria values of less than 300 for adult and child pedestrians.
Design modification on Indian Road Vehicles to Reduce Aerodynamic DragIJAEMSJORNAL
Reducing vehicle fuel consumption has become one of the most important issues in recent years. Aerodynamic drag contributes to 50-60% of fuel consumption in trucks on highways. Vehicle aerodynamic performance is mainly determined by drag coefficient, which directly affects engine requirements and fuel consumption. It’s well known that drag changes in a crosswind compared with a condition without a crosswind, and that the change depends on the vehicle shape. Pressure drag, a major drag for trucks as they run at lower speeds is produced by the shape of the object. Therefore, addition of some components can suffice the need. The vehicle has been designed by using Catia and then analysed with CFD. The values are compared and the resultant drag reduction is calculated.
Comparison of CFD Simulation of a Hyundai I20 Model with Four Different Turbu...IJERA Editor
This article describes the CFD analysis of a Hyundai i20 car Model. The focus of this study is to investigate the
aerodynamics characteristics of Hyundai i20 car model and the flow obtained by solving the steady-state
governing continuity equations as well as the momentum conservation equations combined with one of four
turbulence models (1.Spalart-Allmaras 2.k-ε Standard 3.Transition k-kl-ω 4.Transition Shear Stress Transport
(SST)) and the solutions obtained using these different models were compared. Except transition k-kl-ω model,
other three models show nearly similar velocity variations plot. Pressure variation plot are almost similar with
K-ε and transition-SST models. Eddy viscosity plot are almost similar with K-ε and transition k-kl-ω models.
Car’s Aerodynamic Characteristics at High Speed Influenced by Rear SpoilerIJRES Journal
This study analyzed how different rear spoiler designs influence the aerodynamic characteristics of a car at high speeds. Nine rear spoiler cases were modeled varying the cross-sectional shape, chord length, and horizontal angle. Computational fluid dynamics simulations were run to calculate the aerodynamic lift coefficient for each case. An orthogonal experiment design was used to analyze which factors had the most significant influence on lift. The results showed that cross-sectional shape, chord length, and horizontal angle all had a minor significance. The best combination found was a flat cross-section, 150mm chord length, and 15 degree horizontal angle, which reduced lift the most.
IRJET- Study of Various Passive Drag Reduction Techniques on External Vehicle...IRJET Journal
This document discusses various passive drag reduction techniques that can be used to improve vehicle aerodynamic performance through computational fluid dynamics (CFD) simulations. It classifies techniques such as rear tail flaps, ground effect modifications, diffusers, vortex generators, front bonnet ducts, rear spoilers, and rear fairings. The document provides examples of each technique and references studies showing how they can reduce drag coefficients and improve fuel efficiency when applied to vehicle models in CFD simulations.
This document summarizes research on aerodynamic studies of automobile structures. Nine models were designed and tested in a low-speed wind tunnel at velocities of 15m/s, 20m/s, and 25m/s. The models included forward-facing steps, backward-facing steps, and combinations of the two at inclination angles of 90°, 50°, and 30°. Drag coefficients and pressure distributions on the model surfaces were measured. Drag coefficients generally decreased with lower inclination angles and higher velocities. Pressure distributions showed recirculation zones forming near steps, with more zones observed at lower inclination angles. Previous related research on add-ons to reduce vehicle drag and studies of backward-facing step flows are also summarized.
This document outlines the development of dynamic models to simulate vehicle suspension systems. It begins by describing a basic single degree of freedom model and then progresses to more complex two degree of freedom and four degree of freedom models. Equations of motion are developed for each model. Frequency response functions are presented to demonstrate how damping ratios affect the motion of sprung and unsprung masses. The models and analysis techniques can be used to optimize vehicle damper characteristics before physical testing.
Modification of airflow around a FSAE Race car using sidepods to increase the...EditorIJAERD
Aerodynamics pertaining to vehicles focuses on improving the drive-ability of the vehicle while also reducing
losses due to air drag. This paper focuses on maximizing the cornering performance of the formula student race car with
slight modifications to the airflow around the vehicle and meagre addition of weight. The undertray produces downloads
by altering the velocity of air flowing underneath it. The sidepods act to reduce flow velocity above the undertray, thus
increasing the pressure above it. This leads to an increased pressure difference over the surface of the undertray which
translates to increase in downforce. The car is able to have a 10% decrease in lap times on a 500m racetrack.
Aerodynamic Analysis of Car body with Aerodynamic Devices to Improve PerformanceIRJET Journal
This document discusses a study analyzing the aerodynamic performance of different car body designs through computational fluid dynamics (CFD). Three car body models were analyzed: a bluff model, a streamlined model, and a streamlined model with a rear diffuser. CFD was performed using ANSYS software to calculate drag coefficient, lift coefficient, drag force, and lift force for each model. The results found that the streamlined model with diffuser had the lowest drag coefficient and drag force, indicating improved fuel efficiency compared to the other designs. Adding a rear diffuser also helped to reduce lift and improve stability at high speeds. In conclusion, optimizing the car's shape with streamlining and a diffuser can significantly improve aerod
Aerodynamic Analysis of Car body with Aerodynamic Devices to Improve PerformanceIRJET Journal
This document discusses a study analyzing the aerodynamic performance of different car body designs through computational fluid dynamics (CFD). Three car body models were analyzed: a bluff model, a streamlined model, and a streamlined model with a rear diffuser. CFD was performed using ANSYS software to calculate drag coefficient, lift coefficient, drag force, and lift force for each model. The results found that the streamlined model with diffuser had the lowest drag coefficient and drag force, indicating improved fuel efficiency compared to the other designs. Adding a rear diffuser also helped to reduce lift and improve stability at high speeds. In conclusion, optimizing the car's shape and adding aerodynamic devices like a diffuser can significantly
This document summarizes a study that used computational fluid dynamics (CFD) simulations to analyze how attaching aerodynamic wings to the top of heavy vehicles could increase lift and reduce fuel consumption. The researchers modeled a truck in SolidWorks and simulated airflow over the truck both with and without wings attached. The simulations showed that the wings increased lift by over 4,000 N, reducing the effective weight and correspondingly lowering estimated fuel consumption by 0.34 L/100 km. For a fleet of 15,000 trucks traveling average distances, this could result in annual fuel savings of over $765,000. Therefore, the study demonstrates that aerodynamic lift from wings can meaningfully improve the fuel efficiency of heavy vehicles.
This document provides a technical review of secure banking using RSA and AES encryption methodologies. It discusses how RSA and AES are commonly used encryption standards for secure data transmission between ATMs and bank servers. The document first provides background on ATM security measures and risks of attacks. It then reviews related work analyzing encryption techniques. The document proposes using a one-time password in addition to a PIN for ATM authentication. It concludes that implementing encryption standards like RSA and AES can make transactions more secure and build trust in online banking.
This document analyzes the performance of various modulation schemes for achieving energy efficient communication over fading channels in wireless sensor networks. It finds that for long transmission distances, low-order modulations like BPSK are optimal due to their lower SNR requirements. However, as transmission distance decreases, higher-order modulations like 16-QAM and 64-QAM become more optimal since they can transmit more bits per symbol, outweighing their higher SNR needs. Simulations show lifetime extensions up to 550% are possible in short-range networks by using higher-order modulations instead of just BPSK. The optimal modulation depends on transmission distance and balancing the energy used by electronic components versus power amplifiers.
This document provides a review of mobility management techniques in vehicular ad hoc networks (VANETs). It discusses three modes of communication in VANETs: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and hybrid vehicle (HV) communication. For each communication mode, different mobility management schemes are required due to their unique characteristics. The document also discusses mobility management challenges in VANETs and outlines some open research issues in improving mobility management for seamless communication in these dynamic networks.
This document provides a review of different techniques for segmenting brain MRI images to detect tumors. It compares the K-means and Fuzzy C-means clustering algorithms. K-means is an exclusive clustering algorithm that groups data points into distinct clusters, while Fuzzy C-means is an overlapping clustering algorithm that allows data points to belong to multiple clusters. The document finds that Fuzzy C-means requires more time for brain tumor detection compared to other methods like hierarchical clustering or K-means. It also reviews related work applying these clustering algorithms to segment brain MRI images.
1) The document simulates and compares the performance of AODV and DSDV routing protocols in a mobile ad hoc network under three conditions: when users are fixed, when users move towards the base station, and when users move away from the base station.
2) The results show that both protocols have higher packet delivery and lower packet loss when users are either fixed or moving towards the base station, since signal strength is better in those scenarios. Performance degrades when users move away from the base station due to weaker signals.
3) AODV generally has better performance than DSDV, with higher throughput and packet delivery rates observed across the different user mobility conditions.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
The document proposes a hybrid technique using Anisotropic Scale Invariant Feature Transform (A-SIFT) and Robust Ensemble Support Vector Machine (RESVM) to accurately identify faces in images. A-SIFT improves upon traditional SIFT by applying anisotropic scaling to extract richer directional keypoints. Keypoints are processed with RESVM and hypothesis testing to increase accuracy above 95% by repeatedly reprocessing images until the threshold is met. The technique was tested on similar and different facial images and achieved better results than SIFT in retrieval time and reduced keypoints.
This document studies the effects of dielectric superstrate thickness on microstrip patch antenna parameters. Three types of probes-fed patch antennas (rectangular, circular, and square) were designed to operate at 2.4 GHz using Arlondiclad 880 substrate. The antennas were tested with and without an Arlondiclad 880 superstrate of varying thicknesses. It was found that adding a superstrate slightly degraded performance by lowering the resonant frequency and increasing return loss and VSWR, while decreasing bandwidth and gain. Specifically, increasing the superstrate thickness or dielectric constant resulted in greater changes to the antenna parameters.
This document describes a wireless environment monitoring system that utilizes soil energy as a sustainable power source for wireless sensors. The system uses a microbial fuel cell to generate electricity from the microbial activity in soil. Two microbial fuel cells were created using different soil types and various additives to produce different current and voltage outputs. An electronic circuit was designed on a printed circuit board with components like a microcontroller and ZigBee transceiver. Sensors for temperature and humidity were connected to the circuit to monitor the environment wirelessly. The system provides a low-cost way to power remote sensors without needing battery replacement and avoids the high costs of wiring a power source.
1) The document proposes a model for a frequency tunable inverted-F antenna that uses ferrite material.
2) The resonant frequency of the antenna can be significantly shifted from 2.41GHz to 3.15GHz, a 31% shift, by increasing the static magnetic field placed on the ferrite material.
3) Altering the permeability of the ferrite allows tuning of the antenna's resonant frequency without changing the physical dimensions, providing flexibility to operate over a wide frequency range.
This document summarizes a research paper that presents a speech enhancement method using stationary wavelet transform. The method first classifies speech into voiced, unvoiced, and silence regions based on short-time energy. It then applies different thresholding techniques to the wavelet coefficients of each region - modified hard thresholding for voiced speech, semi-soft thresholding for unvoiced speech, and setting coefficients to zero for silence. Experimental results using speech from the TIMIT database corrupted with white Gaussian noise at various SNR levels show improved performance over other popular denoising methods.
This document discusses group consumption modes. It analyzes factors that impact group consumption, including external environmental factors like technological developments enabling new forms of online and offline interactions, as well as internal motivational factors at both the group and individual level. The document then proposes that group consumption modes can be divided into four types based on two dimensions: vertical (group relationship intensity) and horizontal (consumption action period). These four types are instrument-oriented, information-oriented, enjoyment-oriented, and relationship-oriented consumption modes. Finally, the document notes that consumption modes are dynamic and can evolve over time.
The document summarizes a study of different microstrip patch antenna configurations with slotted ground planes. Three antenna designs were proposed and their performance evaluated through simulation: a conventional square patch, an elliptical patch, and a star-shaped patch. All antennas were mounted on an FR4 substrate. The effects of adding different slot patterns to the ground plane on resonance frequency, bandwidth, gain and efficiency were analyzed parametrically. Key findings were that reshaping the patch and adding slots increased bandwidth and shifted resonance frequency. The elliptical and star patches in particular performed better than the conventional design. Three antenna configurations were selected for fabrication and measurement based on the simulations: a conventional patch with a slot under the patch, an elliptical patch with slots
1) The document describes a study conducted to improve call drop rates in a GSM network through RF optimization.
2) Drive testing was performed before and after optimization using TEMS software to record network parameters like RxLevel, RxQuality, and events.
3) Analysis found call drops were occurring due to issues like handover failures between sectors, interference from adjacent channels, and overshooting due to antenna tilt.
4) Corrective actions taken included defining neighbors between sectors, adjusting frequencies to reduce interference, and lowering the mechanical tilt of an antenna.
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M012438794
1. IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE)
e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 4 Ver. III (Jul. - Aug. 2015), PP 87-94
www.iosrjournals.org
DOI: 10.9790/1684-12438794 www.iosrjournals.org 87 | Page
CFD Simulation of Flow around External Vehicle: Ahmed Body
Saurabh Banga1
, Md. Zunaid2*
, Naushad Ahmad Ansari3
, Sagar Sharma4
,
Rohit Singh Dungriyal5
Assistant Professor, Department of Mechanical Engineering, Delhi Technological University, Bawana Road,
Delhi, India2, 3
U.G Student, Department of Mechanical & Automobile Engineering, Delhi Technological University, Bawana
Road, Delhi, India1,4,5
Abstract: The main objective of this paper is to elucidate a solution to reduce the inefficiencies and losses
caused due to major parameters pertaining to the aerodynamics of road vehicle (drag, lift). This is
accomplished by investigating the variation of the rear slant angle of the Ahmed body and its effect on the drag
and lift coefficients and determine the optimum angle for least drag through numerical simulation. The
simplified vehicle geometry: Ahmed Reference Model has been used as a benchmark. The computational part
consists of numerical simulation of the flow around the Ahmedbody employing CFD (Computational Fluid
Dynamics) techniques. In numerical simulation results, pressure-based solver was utilized and the turbulence
model employed was k-Epsilon realizable model with non-equilibrium wall function for near wall treatment. The
designing of model used in this paper is done through the SOLIDWORKS ‘14; and CFD simulation carried out
in FLUENT (ANSYS 14).
Keywords: Ahmed body, CFD, k-Epsilon realizable model, Drag, Lift
I. Introduction
The pollution emerged by using volatile fuels in automobile has become a major concern pertaining to
the environment and economic viability. Different approaches such as improving the efficiency or usage of
alternative fuels for the vehicle have been considered. Advancement in some of the major areas such as
aerodynamics improvement, weight reduction and power increase has given us many feasible results, but
reducing aerodynamic factors such as drag, lift is more efficient than increasing the power of the vehicle or
decreasing the weight of the vehicle.
Automotive aerodynamics comprises of the study of aerodynamics of road vehicles. Its main goals are
reducing drag, minimizing noise emission, improving fuel economy, preventing undesired lift forces and
minimising other causes of aerodynamic instability at high speeds. Also, in order to maintain better control for
steering and braking, we look into design and aerodynamics of a vehicle. Drag is caused due to the pressure
difference between the frontal and the rear end of the vehicle. It can be reduced by modification of the design of
the vehicle or the modification of the air flow around the vehicle. 50% of the mechanical energy of the vehicle is
wasted to overcome drag at highway speed of nearly 88.5 to 96.5 kph. [1]
It is necessary, at times, to generate down force - to improve traction and thus cornering abilities.Lift
can be dangerous for an automobile, especially at high speeds. So, in order to maintain control for steering and
braking, cars are designed so that the automobile exerts a downward force as their speed increases. However,
increasing this downward force increases drag, which in turn, limits the top speed and increases fuel
consumption. Hence, these two forces must be carefully balanced.
Air has a tendency to curl downwards around the ends of a car, travelling upwards from the high-
pressure region under the car to the low-pressure region on top, at the rear end of the automobile and
subsequently collides with moving low-pressure air. The kinetic energy of these turbulent air spirals acts in a
direction that is negative relative to the direction of travel intended. Thus, the car engine must compensate for
the losses created by this drag. Vortices are released during flow separation and trail downstream to form
structured or unstructured wake patterns. A wake is the region of re-circulating flow immediately behind a
moving or stationary solid body, caused by the flow of surrounding fluid around the body. The local
disturbances in the flow pattern behind the vehicle causes a momentum loss thus causing form drag which
extends far behind the bodyworks of a vehicle.
The generic Ahmed Body reference model has been chosen as the benchmark for carrying out
computations for studying of the aerodynamic parameters. The body was first proposed by Ahmed et al., (1984).
[2]
The Ahmed body is a very simple bluff body which has its shape simple enough to allow for accurate flow
simulation but retains some important practical features relevant to automobile bodies. It has a slant on its rear
end, whose angle can be manipulated and the corresponding drag and lift coefficients calculated. This is done to
exhibit the air flow over the different geometry sections of an automobile and in its vicinity, at different slant
2. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 88 | Page
angles. This model portrays how to calculate the turbulent flow field around a simple car-like geometry using
the turbulent flow, k-epsilon interface.
Different rear slant angles result in the emergence of different wake regions at the rear, which are
mainly responsible for the drag of the vehicle. This paper has the following objectives:
1. To understand the drag and lift mechanism by conducting analysis on Ahmed body with 10 different angle
ranging from 0-40 degrees.
2. To exhibit and comprehend the velocity contours, focussing at the wake region of the body.
3. To portray pressure distribution over the entire Ahmed body.
II. Literature Review
Ahmed et al. (1984) [2]
analysed time averaged wake structure around the Ahmed body at a Reynolds
number equal to 1.2*106
by manipulating the rear slant angle in the range of 0-400
in increments of 50
. However,
the study did not yield information about unsteady flow characteristics of the flow around the Ahmed body.
Bayraktar et al. (2001) [3]
examined the external aerodynamics of Ahmed reference body for the rear
slant angles of 0, 12.5, and 25 degrees. The main concern was observing the effect on the lift and drag
coefficients due to variation of Reynolds number and calculating wind-averaged drag coefficients. The 10-inch
water column possessing an electronic scanning module coupled with a force balance system was utilized to
measure the pressure and forces which are consequently used to calculate the drag coefficients.
Spohn and Gillieron (2002) [4]
carried out experiments to investigate the flow characteristics of the
Ahmed body with the slant angle equal to 25 degree and the Reynolds number equal to 8.3*103
. The experiment
was carried out in a closed water tunnel, using the electrolyte precipitation technique at the front as well as the
rear of the Ahmed body.
M. Zunaid, Naushad Ahmad Ansari [5]
designed and implemented the curved boat tail configuration
without the AFC device on a generic SUV design working on the principle of Coanda effect, causing the airflow
over and under the SUV to take a curved path resulting in blowing of air in the immediate wake region. They
examined its effect on various aerodynamic parameters and reported an increase in the average pressure in the
wake region along with a significant drag reduction of 8.013 %.
Morelli et al. (1976) conceptualized and proposed a theoretical method to determine the optimum shape
of a passenger car body for minimum drag by imposing the condition that the total lift be zero. This study
proved that the aerodynamic drag can be reduced substantially without utilizing any additional devices by
optimizing the body shape. Morelli et al. (2000) [6]
proposed a new technique called “fluid tail”, obtainable by
addressing small power air jets in the wake, for application to the aerodynamic design of basic shape of a
passenger car. .
P. Drage et al (2008) [7]
conducted both CFD simulations as well as wind tunnel testing (T.U Graz wind
tunnel) on the Ahmed body with two rear slant angle configurations. The simulation was performed with the
Fluent and by using the Reynold Stress Model. The mesh was developed with the meshing tool SPIDER. It
consisted of 4 prism layers around the body and had an unstructured volume mesh giving a total cell count of
7.7 million cells. This type of meshing approach is commonly adopted as the time spent to create a structured
grid around real vehicle shapes would prevent engineers from operating within the strict deadlines imposed by
vehicle design cycles. For the 25° angle, a drag coefficient of 0.299 and a lift coefficient of 0.345 was obtained
from the wind tunnel experiment, while the CFD simulation resulted in the values of 0.295 and 0.387 for drag
and lift coefficient respectively. The RSM model showed an over estimation of the pressure coefficient over the
slant angle, when compared to the pressure measurement made by Lienhart and Becker (2003). [8]
Figure 1: Geometry of Ahmed model
3. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 89 | Page
Han (1992) [9]
performed aerodynamic shape optimization on Ahmed body with three shape
parameters: backlight angle (0º to 30º), boat tail angle (0º to 30º) and ramp angle (0º to 20º). The k-ε turbulence
model CFD solver was coupled with an optimization routine. In this study, an analytic approximation function
of the objective function (drag coefficient values from CFD 28 analysis) was created in terms of the design
variables. The optimization was then performed on this approximation function and optimum parameters were
found. The CFD analysis was again performed with this optimum set of parameters and the objective function
was updated with new results. This process was continued until the parameters for minimum drag were
obtained. The optimization process revealed that the optimum rear body parameters are backlight angle of 17.80
;
boat-tail angle of 18.90
; and ramp angle of 9.20
. The determined values for minimum drag were found to lie
within the experimentally determined values of 15-180
backlight angles, 15-220
boat-tail angles and 9-140
ramp
angles. The drag coefficient was reduced from 0.209 for a square back to 0.110 for an optimized geometry.
However, the technique used for parameterization of geometry in this study cannot be applied to complex
geometries.
S. Kapadia et. al.[10]
conducted CFD analysis on the Ahmed body with the 25° slant angle configuration
using two different turbulence modelling approaches: Detached eddy simulation (DES) and single equation
unsteady RANS model. An unstructured volume mesh grid of 1.7 million cells was generated with Gridgen and
COBALT was used as a solver. Although both the models predict the presence of the counter rotating vortices,
the DES depicted a better representation of the unsteady structure at the trailing edge of the Ahmed body. The
drag coefficient reached a constant value after approximately 3 seconds of simulation for both DES and RANS.
DES showed an average Cd value of 0.2585 while with the RANS approach the drag the average Cd calculated
is 0.3272.
III. Numerical Simulation
The reference Ahmed Body is 1044mm long, 327mm wide and 288mm high. In ANSYS „14 Design
Modeller, a single body domain of air is created surrounding the Ahmed body walls after subtracting it from the
air enclosure. It has dimensions 5m from front, 7.5m from the rear and 3m from the top.
Figure 2: Single air body domain
3.1 Meshing
The “finite element method” technique is used in our problem. The ANSYS Meshing Tool is used for
carrying out the meshing. The model is 50 mm above the floor.
Details of the mesh are as follows: Relevance center: coarse, Smoothing: high, Transition: slow, Initial size
seed: Active assembly, Min. size: 1mm, Max. Size: 250mm, Advanced Size function: Proximity and Curvature.
Modifications in meshing:
4. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 90 | Page
Size of roller meshing is limited to 2mm.
Size of faces meshing is limited to 10mm.
Inflation Layer method [11]
of first aspect ratio of 5, growth rate of 20% of 5 layers is used.
3 different volumetric limit size boxes are created:
1. Car Box: Limits the size of mesh around Ahmed Body up to 15mm.
2. Wake Box: Limits the size of mesh around wake region up to 10mm.
3. Underbody Box: Limits the size of mesh under the body up to 10mm.
The mesh is composed of 2112223 tetrahedral elements. Figure 4 shows the generated mesh.
Figure 3: Mesh of Ahmed body
3.2 Steady Flow Numerical Simulation:
Computational resources for the steady flow numerical simulations are a Dell workstation (1 CPU 1.8
GHz and 8GB RAM) and Windows 8 OS.
Realizable k-epsilon model with non-equilibrium wall function for near wall treatment is used with
Inlet velocity V = 40m/s and turbulence intensity is about 1% and turbulence viscosity ratio is 10 at inlet,
turbulence intensity is about 5% and turbulence viscosity ratio is 10 at outlet. Density of air is 1.225 kg/m3
,
temperature is 288.16 K and viscosity is 1.7894e-05
kg/m4
. Boundary conditions are - uniform velocity at inlet,
uniform pressure at outlet, symmetry at lateral and at top wall of the model and moving wall at floor.
Solution method utilizes pressure-velocity coupling scheme as coupled with gradient: least square cell
based method, pressure as standard and setting the momentum, turbulence kinetic energy, turbulence dissipation
rate as first order upwind for the initial 100 iterations and correspondingly as second order upwind for the next
500 iterations. Moreover, turbulence viscosity factor is taken as 0.8 for the initial 100 iterations and
consequently taken as 0.95 for the remaining 500 iterations.
IV. Simulation Results
The drag and lift coefficients are calculated for the 10 different manipulations of rear slant angle of the
Ahmed body ranging from 00-
400
. The minimum drag is obtained for the rear slant angle, φ= 7.5 degree for the
attached flow range of angles which exists up to 300
and thereafter, the flow becomes unattached at rear slant
and correspondingly the values of drag and lift tend to be randomly dispersed.
5. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 91 | Page
Table 1: Steady flow numerical simulation results
The table portrays our findings indicating that drag coefficient continually decreases from 00
reaching a
minimum at 7.50
and then continually increases for the attached flow range up to 300
.
Moreover, the lift coefficient linearly increases as the rear slant angle is increased from 00
up till 300
transitioning from negative (also called „downforce‟) to positive value of lift. The lift coefficient approaches
zero value at 7.50
. [12]
Figure 4: Graph between drag & lift coefficients and different rear slant angles
The drag and lift coefficients are plotted on a graph (above). It is observed that the lift coefficient
follows a linear increasing trend for rear slant angle ranging 0-200
. The minimum positive lift of 0.0292 is
obtained for rear slant angle of 7.50
. Also, the drag coefficient decreases as rear slant is increased from 00
up to
7.50
, where it reaches the minimum value of 0.2346 and then continually goes on increasing till 300
.
Beyond 300
, flow separation occurs and evidently drag and lift coefficient become randomly dispersed.
Rear slant angle (φ) (In degrees) Cd Cl
0 2.50031e-01 -1.17457e-01
5 2.37215e-01 -1.49709e-02
7.5 2.34631e-01 2.92149-02
10 2.36738e-01 8.29710e-02
12.5 2.41644e-01 1.32483e-01
15 2.46833e-01 1.85001e-01
20 2.61934e-01 2.83622e-01
30 2.97872e-01 3.47783e-01
35 2.94980e-01 2.05502e-01
40 2.50360e-01 8.36791e-03
6. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 92 | Page
4.1 Velocity contours
Figure 5: Velocity Contours at different rear slant angles
Gives us the velocity of air along different geometry sections of the Ahmed body. The green area
corresponds to the velocity 40m/sec, while blue area show low velocity and high pressure region and red area
gives high velocity low pressure region.
The velocity contours clearly indicate that the wake region, and consequently the form drag,
continually decreases as the rear slant angle is increased from 0-300
and thereafter, boundary layer separation
occurs on the rear slant. However, there is an increase in lift with increase in rear slant angle due to larger
pressure difference generated between top and bottom surfaces of the vehicle, and this results in larger lift-
induced drag. So, a trade-off between these two drag mechanisms is done to determine the optimum angle
giving minimum drag coefficient.
As the wake area is reduced, the drag-causing eddies (vortices), generated due to the pressure
difference between the top and bottom of the Ahmed body at the rear trailing end, come closer together. This
results in less kinetic energy being dissipated due to these smaller eddies and consequently less compensation
power required by the engine to propel the vehicle forward. It results in higher pressure being applied at the rear
surface of the body and consequently less form drag.
7. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 93 | Page
4.2 Pressure distribution
Figure 6: Pressure Distribution at different rear slant angles
The air becomes almost stagnant as it strikes the vehicle which results in air exerting very high pressure
on front engine grill of the vehicle represented by the red area. The airflow then gets divided between the upper
and lower surface of the vehicle. The higher pressure air on front surface accelerates as it travels over the curved
nose surface of Ahmed body, causing the pressure to drop. This lower pressure creates lifts over the roof surface
as the air passes over it. As the air continues to flow and make its way to the rear, a notch is created by the rear
slant owing to flow separation, leaving a vacuum or low pressure space which the air is not able to fill properly.
The resulting lower pressure creates lift that then acts upon the surface area of the rear slant.
For the multifarious slant angles, it is evident that at the initial section of the rear slant, the pressure
goes on increasing (evident by the decreasing green area) with decreasing value of rear slant angle from 300
-00
.
This is due to less dramatic change in the direction of airflow, resulting in decreased formation of notch (low
pressure or vacuum region). This results in more equalized pressure between the top and bottom surfaces of the
Ahmed body and hence, reduced tendency of lift.
5 degree slant angle
8. CFD Simulation Of Flow Around External Vehicle: Ahmed Body
DOI: 10.9790/1684-12438794 www.iosrjournals.org 94 | Page
V. Conclusion
CFD results for multifarious manipulations of the rear slant angle of the Ahmed Body are presented
after the geometries are designed and then developed. Comparison and examination by plotting a graph of the
lift and drag coefficients obtained for the numerous manipulations is done to determine the optimum rear slant
angle giving minimum drag coefficient. The following conclusions can be drawn from the results:
1. The minimum coefficient of drag (Cd) of 0.2346 is obtained with configuration of Ahmed Body with 7.5
degree rear slant angle.
2. The drag increases as the rear slant angle is reduced and increased from 7.50
down to 00
and up to 300
respectively.
3. The minimum positive coefficient of lift (Cl) of 0.0292 is obtained with configuration of Ahmed Body
with 7.5 degree rear slant angle.
4. The lift coefficient constantly goes on increasing with increasing rear slant angle, for the attached flow
range and it follows an almost linear trend for the 00
-200
range of angles, becoming non-linear thereafter.
5. The drag and lift coefficient becomes randomly dispersed after the flow becomes unattached after
increasing rear slant angle to 300
and beyond.
References
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