This document summarizes research on vortex shedding and its effects on tall, cylindrical structures. It defines vortex shedding as alternating low pressure zones that form on the downwind side of a structure due to wind, causing vibrations. These vibrations can be damaging if they match the structure's natural frequency. The document outlines methods for analyzing the risk of vortex shedding, including calculating the vortex shedding frequency and comparing it to the structure's natural frequencies. It also discusses ways to address vortex shedding in design, such as adding strakes or changing the structure's geometry.
This document summarizes research on the flow past bluff bodies at different Reynolds numbers. It outlines the experimental setup using a circular cylinder in a towing tank and hydrogen bubble visualization. Results show laminar flow with attached vortices at low Re, onset of von Karman vortex shedding at Re=47-90, and pure vortex shedding above Re=90. Vortex size, frequency, separation angle, and other properties change with Re. Future work proposed investigating more regimes experimentally and numerically and other applications of von Karman vortex shedding.
Vortex Shedding Study using Flow visualisation Lavish Ordia
This document summarizes a study that used flow visualization experiments to examine vortex formation behind various blunt bluff body shapes placed inside a circular pipe. Dye injection was used to visualize complex vortex patterns. Parameters like Strouhal number, vortex formation length, and wake width were measured for different orientations and shapes, including modifications to a trapezoidal cylinder. Both interacting and non-interacting vortex formation with shear layers was observed. The document provides background on the experimental setup and image processing methods used to analyze vortex shedding frequencies and lengths.
The document discusses turbulence in fluid flows. It defines types of flow based on the Reynolds number and describes characteristics of turbulent flows such as randomness, nonlinearity, diffusivity, and vorticity. It provides a brief history of turbulence research, discussing early work by Reynolds, Taylor, Prandtl, von Karman, and Richardson. It also describes concepts such as Reynolds stresses, magnitude and intensity of turbulence, and smooth and rough pipe boundaries.
We have come up as one of the most reliable as well as prominent Exporters and Suppliers of Vortex Gas Flow Meters in New Delhi. The Vortex Gas Flow Meters, offered by the company, are feature-studded products with a guarantee of quality. These Vortex Gas Flow Meters are known for their durability as well high efficiency.
Highlights Of Vortex Gas Flow Meters
Stable long term accuracy and repeatability
No routine maintenance required
Lower cost of installation than traditional orifice-type meters
Reduced possibility of process fluid leakage
No moving parts to wear
No special protection needed against extreme weather condition
Specifications
Size DN 25 to DN 3000
Service Liquid / Gas / Steam
Pressure 25 bar
Output Signal 4-20 mA
Communication Interface RS485
Accuracy + / - 0.5%, + / - 1%
Repeatability 0.2%
Protection IP 65 / IP 68
Numerical and experimental investigation of co shedding vortex generated by t...Alexander Decker
The document investigates the effect of co-shedding vortices generated by two adjacent circular cylinders on air flow behavior around an NACA 2412 airfoil. Both experimental and numerical methods were used. Experimentally, a smoke wind tunnel was used to visualize flow at different velocities and angles of attack. Numerically, ANSYS was used to simulate results. The study found that the vortices induced turbulence upstream of the airfoil, preventing separation and allowing reattachment of the flow. Both methods showed that increasing angle of attack or velocity shifted the separation point toward the leading edge. The vortices generated by the cylinders thus helped control flow separation around the airfoil.
This document is Emeka Chijioke's engineering diploma thesis on numerically modelling the laminar to turbulent flow transition in a compressor cascade. It was advised by Dr. Sławomir Kubacki and submitted to the Warsaw University of Technology's Faculty of Power and Aeronautical Engineering in January 2012. The thesis aims to numerically calculate and understand the flow behavior over a NACA 65 series airfoil using computational fluid dynamics software and correlate the results with experimental data from a previous study on flow transition. The thesis includes chapters on the governing equations, computational details, results and discussion, and conclusions.
IRJET- CFD Simulation of Transitional Flow Across Pak B Turbine BladesIRJET Journal
This document discusses computational fluid dynamics (CFD) simulation of transitional flow across PAK-B turbine blades. It begins by introducing the challenges of modeling transitional flows which contain both laminar and turbulent regions. It then provides background on laminar-turbulent transition, noting it is influenced by factors like free-stream turbulence, pressure gradients, and flow separation. The document evaluates using RANS-based CFD codes with transition models to analyze transitional flow over a PAK-B airfoil, validating results against experimental surface pressure and flow data. The goal is demonstrating existing transition and turbulence models' ability to predict transitional flows past isolated airfoils.
Advanced Simulations of Hypertrophic Obstructive Cardiomyopathy in Human Hear...Can Ozcan
Surgeons, physicians and biomedical engineers need a model to better understand heart mechanics and develop solutions around it. Such modeling effort needs to incorporate multiphysics and nonlinearity where Ansys can help.
This presentation is a continuation of what has been done last year using simplified conditions. 3D two-way fully coupled fluid-structure interaction with viscoelastic valve motion in human heart left ventricle is resolved using realistic boundary conditions and material properties.
Can holds BS and MS degrees in Mechanical Engineering and currently a PhD candidate in Biomedical Engineering from Bogazici University Istanbul. He has been with Ozen Engineering since 2005, where he has been performing structural and fluid dynamics simulations using Ansys in various fields. Can is using Python heavily to develop solutions around Ansys products.
This document summarizes research on the flow past bluff bodies at different Reynolds numbers. It outlines the experimental setup using a circular cylinder in a towing tank and hydrogen bubble visualization. Results show laminar flow with attached vortices at low Re, onset of von Karman vortex shedding at Re=47-90, and pure vortex shedding above Re=90. Vortex size, frequency, separation angle, and other properties change with Re. Future work proposed investigating more regimes experimentally and numerically and other applications of von Karman vortex shedding.
Vortex Shedding Study using Flow visualisation Lavish Ordia
This document summarizes a study that used flow visualization experiments to examine vortex formation behind various blunt bluff body shapes placed inside a circular pipe. Dye injection was used to visualize complex vortex patterns. Parameters like Strouhal number, vortex formation length, and wake width were measured for different orientations and shapes, including modifications to a trapezoidal cylinder. Both interacting and non-interacting vortex formation with shear layers was observed. The document provides background on the experimental setup and image processing methods used to analyze vortex shedding frequencies and lengths.
The document discusses turbulence in fluid flows. It defines types of flow based on the Reynolds number and describes characteristics of turbulent flows such as randomness, nonlinearity, diffusivity, and vorticity. It provides a brief history of turbulence research, discussing early work by Reynolds, Taylor, Prandtl, von Karman, and Richardson. It also describes concepts such as Reynolds stresses, magnitude and intensity of turbulence, and smooth and rough pipe boundaries.
We have come up as one of the most reliable as well as prominent Exporters and Suppliers of Vortex Gas Flow Meters in New Delhi. The Vortex Gas Flow Meters, offered by the company, are feature-studded products with a guarantee of quality. These Vortex Gas Flow Meters are known for their durability as well high efficiency.
Highlights Of Vortex Gas Flow Meters
Stable long term accuracy and repeatability
No routine maintenance required
Lower cost of installation than traditional orifice-type meters
Reduced possibility of process fluid leakage
No moving parts to wear
No special protection needed against extreme weather condition
Specifications
Size DN 25 to DN 3000
Service Liquid / Gas / Steam
Pressure 25 bar
Output Signal 4-20 mA
Communication Interface RS485
Accuracy + / - 0.5%, + / - 1%
Repeatability 0.2%
Protection IP 65 / IP 68
Numerical and experimental investigation of co shedding vortex generated by t...Alexander Decker
The document investigates the effect of co-shedding vortices generated by two adjacent circular cylinders on air flow behavior around an NACA 2412 airfoil. Both experimental and numerical methods were used. Experimentally, a smoke wind tunnel was used to visualize flow at different velocities and angles of attack. Numerically, ANSYS was used to simulate results. The study found that the vortices induced turbulence upstream of the airfoil, preventing separation and allowing reattachment of the flow. Both methods showed that increasing angle of attack or velocity shifted the separation point toward the leading edge. The vortices generated by the cylinders thus helped control flow separation around the airfoil.
This document is Emeka Chijioke's engineering diploma thesis on numerically modelling the laminar to turbulent flow transition in a compressor cascade. It was advised by Dr. Sławomir Kubacki and submitted to the Warsaw University of Technology's Faculty of Power and Aeronautical Engineering in January 2012. The thesis aims to numerically calculate and understand the flow behavior over a NACA 65 series airfoil using computational fluid dynamics software and correlate the results with experimental data from a previous study on flow transition. The thesis includes chapters on the governing equations, computational details, results and discussion, and conclusions.
IRJET- CFD Simulation of Transitional Flow Across Pak B Turbine BladesIRJET Journal
This document discusses computational fluid dynamics (CFD) simulation of transitional flow across PAK-B turbine blades. It begins by introducing the challenges of modeling transitional flows which contain both laminar and turbulent regions. It then provides background on laminar-turbulent transition, noting it is influenced by factors like free-stream turbulence, pressure gradients, and flow separation. The document evaluates using RANS-based CFD codes with transition models to analyze transitional flow over a PAK-B airfoil, validating results against experimental surface pressure and flow data. The goal is demonstrating existing transition and turbulence models' ability to predict transitional flows past isolated airfoils.
Advanced Simulations of Hypertrophic Obstructive Cardiomyopathy in Human Hear...Can Ozcan
Surgeons, physicians and biomedical engineers need a model to better understand heart mechanics and develop solutions around it. Such modeling effort needs to incorporate multiphysics and nonlinearity where Ansys can help.
This presentation is a continuation of what has been done last year using simplified conditions. 3D two-way fully coupled fluid-structure interaction with viscoelastic valve motion in human heart left ventricle is resolved using realistic boundary conditions and material properties.
Can holds BS and MS degrees in Mechanical Engineering and currently a PhD candidate in Biomedical Engineering from Bogazici University Istanbul. He has been with Ozen Engineering since 2005, where he has been performing structural and fluid dynamics simulations using Ansys in various fields. Can is using Python heavily to develop solutions around Ansys products.
This presentation is given at Santa Clara Ansys Conference in 2014, where we have presented the viscoelastic modelling capabilities in Ansys and the basic requirements for such modelling. The presentation is simple and a good starting point to understand viscoelastic modeling in Ansys.
Turbulent flows are characterized by chaotic, unpredictable changes in velocity. The document discusses turbulence, including defining turbulence, the transition from laminar to turbulent flow, Reynolds averaging to decompose variables into mean and fluctuating components, and the effects of turbulence on the Navier-Stokes equations. It also examines Reynolds stresses, time-averaged conservation equations for turbulent flow, and modeling approaches like Reynolds averaging to account for turbulent fluctuations and closure problems in the equations.
IRJET- Analysis of Two Phase Flow Induced Vibration in Piping SystemsIRJET Journal
1. The document analyzes two-phase flow induced vibration in piping systems. It develops the governing dynamic equation and stiffness/inertia matrices for a pipe conveying fluid.
2. Four boundary conditions are considered: pinned-pinned, clamped-pinned, clamped-clamped, and clamped-free. Analytical and finite element methods are used to find natural frequencies under different conditions.
3. Pipe buckling or divergence is observed at higher fluid velocities for some boundary conditions. The critical velocity at which buckling starts is identified. Natural frequency diminishes at the onset of divergence for some cases.
An introduction to vortex-flows and their implications on solid-liquid separa...Hydro International
There is often ambiguity in what constitutes vortex behaviour, and common descriptions are qualitative in nature and therefore necessarily limited. It has become common to identify quantitative features associated with vortices in order to provide a definition.
A full understanding of real-world vortex behaviour enables engineers to develop hydrodynamic separators that minimise short circuiting and maximise the residence time of the fluid, ensuring that the best use is made of the available volumes. With this understanding, separation units can be designed to be resistant to changes in inflow conditions, enabling them to collect a wide range of materials across a wide range of flow rates.
Major losses, also known as frictional losses, occur in pipes due to the viscous effects of fluid and roughness of pipe walls. These losses are associated with the frictional energy lost as fluid flows. There are two types of fluid flow - laminar and turbulent - which have different laws of friction. The Darcy-Weisbach equation can be used to calculate frictional loss. It relates head loss to flow characteristics like velocity, pipe dimensions, fluid properties and roughness.
This document provides 5 examples of calculating discharge over notches of different shapes. Example 1 calculates discharge over a rectangular notch. Example 2 calculates the length of a rectangular notch given the discharge. Example 3 calculates discharge over a triangular notch. Example 4 calculates discharge over a trapezoidal notch. Example 5 calculates the depth of water required over a triangular notch to produce the same discharge as a rectangular notch. Formulas and step-by-step workings are shown for each example calculation.
This document discusses fluid-induced vibration (FIV) in heat exchangers. It covers topics like vortex shedding, synchronization, critical velocity, fluid-elastic instability, and vibration damage patterns. The key points are:
- Vortex shedding from cylindrical structures can cause fluid excitation forces at the shedding frequency, and fluid-structure coupling forces if that frequency matches structural natural frequencies.
- There is a critical cross-flow velocity at which fluid-elastic instability occurs, causing rapid increases in vibration amplitude.
- Vibration damage in heat exchangers can include tube collisions, baffle damage, tube sheet effects, and acoustic resonance failures.
This document discusses concepts related to fluid flow through circular conduits including:
- Laminar flow through pipes and boundary layer concepts such as boundary layer thickness.
- The Darcy-Weisbach equation for calculating head loss and how it relates to friction factor.
- The Moody diagram which plots friction factor against Reynolds number for different relative pipe roughnesses.
- Commercial pipes and how piping systems are used to transport fluids with considerations for energy loss due to friction.
Introduction to Stress Analysis and Piping Vibration AnalysisAndré Fraga
This slide is a short introduction to Piping Stress Analysis and Piping Vibration Analysis. It was made as a resume to introduce new Engineers to this subject.
Flow Over A Sharp Crested Weir ExperimentFarhan Sadek
This slide gives a short overview on the experiment mentioned above of Fluid Mechanics (sessional) course which is generally taught in Civil Engineering and Mechanical Engineering.
Contents:
- Introduction
- Theoretical Background
- Methods
- Result
- Application
- Conclusion & Discussion
Flow can be defined as the quantity of fluid passing a point per unit time. Flow rate is affected by properties like fluid velocity, pipe size, friction, viscosity, and specific gravity. Ultrasonic flow meters use ultrasound to measure flow velocity and calculate volumetric flow rate. They work well for clean liquids and are unaffected by temperature, density, or viscosity changes. Electromagnetic flow meters use Faraday's law of induction - the voltage induced across a conductor moving through a magnetic field is proportional to its velocity. Thermal flow meters are based on conductive and convective heat transfer - a heated wire in fluid flow measures mass velocity according to King's law. They are mainly used for low pressure gas flow measurement.
Flow-induced vibration in heat exchangers has been a major problem for decades. Three main mechanisms that cause vibration are fluid-elastic instability, vortex shedding, and multi-phase buffeting. Fluid-elastic instability is the most important mechanism for shell and tube heat exchangers. Several studies have analyzed vibration experimentally and through computational fluid dynamics simulations. Parameters like damping ratios, tube properties, fluid properties, and flow velocities are important factors in vibration analysis and predicting the onset of instability.
This document discusses various types of pressure transducers, including mechanical and electrical types. Mechanical transducers use an elastic element like a bourdon tube, bellows, or diaphragm to convert pressure to displacement. Electrical transducers add an electric element to convert the mechanical displacement to an electrical signal. Common electric elements are piezoelectric materials, strain gauges, capacitors, and inductive coils. Piezoelectric transducers actively generate a voltage in response to pressure, while other electrical transducers like strain gauges are passive and require an external power source to modulate their electrical properties.
This document discusses flow through pipes, including:
- Laminar and turbulent flow characteristics defined by Reynolds number
- Head losses calculated using Darcy-Weisbach and minor loss equations
- Friction factors determined from Moody diagrams for laminar and turbulent flows
- Total head loss in a pipe system equals major losses in pipe sections plus minor losses from fittings
This document discusses energy losses that occur in hydraulic systems. It begins by defining laminar and turbulent flows, and introduces the Reynolds number which determines the type of flow. It then explains that greater energy losses occur in turbulent flow compared to laminar flow. The document goes on to describe the Darcy-Weisbach equation for calculating head losses due to friction in pipes. Specific equations are provided to calculate losses for laminar and turbulent flow, taking into account factors like pipe roughness and Reynolds number. The purpose is to analyze energy losses that occur in components like valves and fittings so they can be properly accounted for in system design.
120218 chapter 8 momentum analysis of flowBinu Karki
The document discusses momentum analysis of fluid flow. It contains the following key points:
1) The momentum equation is based on the law of conservation of momentum, which states that the net force acting on a fluid mass is equal to the rate of change of momentum of the fluid.
2) The momentum principle can be written as an impulse-momentum equation: the impulse of a force acting on a fluid mass over a short time interval is equal to the change in momentum of the fluid.
3) The momentum equation is used to determine the resultant force exerted by a flowing fluid on a pipe bend based on the fluid's velocity, pressure, area, and external forces at two sections of the pipe.
Overview of the Vortex Flow Meter product range from Badger Meter including technical data. This presentation also explains vortex shedding technology.
This document discusses pipe friction and flow experiments. It defines key terms like friction factor, Reynolds number, laminar and turbulent flow. The objective is to use a Moody diagram to determine these variables and the relative roughness of a pipe. Sample calculations are shown for one data point. The methodology involves using the Darcy-Weisbach equation and Moody diagram. Potential errors include human errors in measurement and recording. The conclusion is that all flows studied were turbulent based on their high Reynolds numbers, and that friction factors decrease while head losses increase with higher densities and velocities.
Energy generation from vortex induced vibrations reporteor20104
This document discusses energy generation from vortex induced vibrations of bluff bodies in fluid flows. It describes how vortices form behind bluff bodies at certain flow speeds, creating periodic lift forces that can induce structural vibration. This vibration can be harnessed to extract energy through mechanisms attached to vibrating structures. Specifically, at certain flow speeds vortex shedding frequency locks in with the structure's natural frequency, amplifying vibrations and making more energy available for harvesting. The document provides theoretical background on vortex formation, shedding frequency, lock-in phenomena, and the effect of boundary gaps near structures.
IRJET- Tall-Building Structure Shape Optimization using “Computational Fluid ...IRJET Journal
This document discusses using computational fluid dynamics (CFD) to optimize the shape of tall buildings to reduce wind pressure. It begins by introducing CFD simulation as a suitable method for analyzing how wind pressure is affected by different building shapes. The document then provides background on wind forces on tall buildings and how wind flow patterns are complex. It describes using the realizable k-ε turbulent model in ANSYS software to simulate turbulent wind flow for the CFD analysis. The summary analyzes different building shapes using CFD to select a shape with reduced wind pressure.
This presentation is given at Santa Clara Ansys Conference in 2014, where we have presented the viscoelastic modelling capabilities in Ansys and the basic requirements for such modelling. The presentation is simple and a good starting point to understand viscoelastic modeling in Ansys.
Turbulent flows are characterized by chaotic, unpredictable changes in velocity. The document discusses turbulence, including defining turbulence, the transition from laminar to turbulent flow, Reynolds averaging to decompose variables into mean and fluctuating components, and the effects of turbulence on the Navier-Stokes equations. It also examines Reynolds stresses, time-averaged conservation equations for turbulent flow, and modeling approaches like Reynolds averaging to account for turbulent fluctuations and closure problems in the equations.
IRJET- Analysis of Two Phase Flow Induced Vibration in Piping SystemsIRJET Journal
1. The document analyzes two-phase flow induced vibration in piping systems. It develops the governing dynamic equation and stiffness/inertia matrices for a pipe conveying fluid.
2. Four boundary conditions are considered: pinned-pinned, clamped-pinned, clamped-clamped, and clamped-free. Analytical and finite element methods are used to find natural frequencies under different conditions.
3. Pipe buckling or divergence is observed at higher fluid velocities for some boundary conditions. The critical velocity at which buckling starts is identified. Natural frequency diminishes at the onset of divergence for some cases.
An introduction to vortex-flows and their implications on solid-liquid separa...Hydro International
There is often ambiguity in what constitutes vortex behaviour, and common descriptions are qualitative in nature and therefore necessarily limited. It has become common to identify quantitative features associated with vortices in order to provide a definition.
A full understanding of real-world vortex behaviour enables engineers to develop hydrodynamic separators that minimise short circuiting and maximise the residence time of the fluid, ensuring that the best use is made of the available volumes. With this understanding, separation units can be designed to be resistant to changes in inflow conditions, enabling them to collect a wide range of materials across a wide range of flow rates.
Major losses, also known as frictional losses, occur in pipes due to the viscous effects of fluid and roughness of pipe walls. These losses are associated with the frictional energy lost as fluid flows. There are two types of fluid flow - laminar and turbulent - which have different laws of friction. The Darcy-Weisbach equation can be used to calculate frictional loss. It relates head loss to flow characteristics like velocity, pipe dimensions, fluid properties and roughness.
This document provides 5 examples of calculating discharge over notches of different shapes. Example 1 calculates discharge over a rectangular notch. Example 2 calculates the length of a rectangular notch given the discharge. Example 3 calculates discharge over a triangular notch. Example 4 calculates discharge over a trapezoidal notch. Example 5 calculates the depth of water required over a triangular notch to produce the same discharge as a rectangular notch. Formulas and step-by-step workings are shown for each example calculation.
This document discusses fluid-induced vibration (FIV) in heat exchangers. It covers topics like vortex shedding, synchronization, critical velocity, fluid-elastic instability, and vibration damage patterns. The key points are:
- Vortex shedding from cylindrical structures can cause fluid excitation forces at the shedding frequency, and fluid-structure coupling forces if that frequency matches structural natural frequencies.
- There is a critical cross-flow velocity at which fluid-elastic instability occurs, causing rapid increases in vibration amplitude.
- Vibration damage in heat exchangers can include tube collisions, baffle damage, tube sheet effects, and acoustic resonance failures.
This document discusses concepts related to fluid flow through circular conduits including:
- Laminar flow through pipes and boundary layer concepts such as boundary layer thickness.
- The Darcy-Weisbach equation for calculating head loss and how it relates to friction factor.
- The Moody diagram which plots friction factor against Reynolds number for different relative pipe roughnesses.
- Commercial pipes and how piping systems are used to transport fluids with considerations for energy loss due to friction.
Introduction to Stress Analysis and Piping Vibration AnalysisAndré Fraga
This slide is a short introduction to Piping Stress Analysis and Piping Vibration Analysis. It was made as a resume to introduce new Engineers to this subject.
Flow Over A Sharp Crested Weir ExperimentFarhan Sadek
This slide gives a short overview on the experiment mentioned above of Fluid Mechanics (sessional) course which is generally taught in Civil Engineering and Mechanical Engineering.
Contents:
- Introduction
- Theoretical Background
- Methods
- Result
- Application
- Conclusion & Discussion
Flow can be defined as the quantity of fluid passing a point per unit time. Flow rate is affected by properties like fluid velocity, pipe size, friction, viscosity, and specific gravity. Ultrasonic flow meters use ultrasound to measure flow velocity and calculate volumetric flow rate. They work well for clean liquids and are unaffected by temperature, density, or viscosity changes. Electromagnetic flow meters use Faraday's law of induction - the voltage induced across a conductor moving through a magnetic field is proportional to its velocity. Thermal flow meters are based on conductive and convective heat transfer - a heated wire in fluid flow measures mass velocity according to King's law. They are mainly used for low pressure gas flow measurement.
Flow-induced vibration in heat exchangers has been a major problem for decades. Three main mechanisms that cause vibration are fluid-elastic instability, vortex shedding, and multi-phase buffeting. Fluid-elastic instability is the most important mechanism for shell and tube heat exchangers. Several studies have analyzed vibration experimentally and through computational fluid dynamics simulations. Parameters like damping ratios, tube properties, fluid properties, and flow velocities are important factors in vibration analysis and predicting the onset of instability.
This document discusses various types of pressure transducers, including mechanical and electrical types. Mechanical transducers use an elastic element like a bourdon tube, bellows, or diaphragm to convert pressure to displacement. Electrical transducers add an electric element to convert the mechanical displacement to an electrical signal. Common electric elements are piezoelectric materials, strain gauges, capacitors, and inductive coils. Piezoelectric transducers actively generate a voltage in response to pressure, while other electrical transducers like strain gauges are passive and require an external power source to modulate their electrical properties.
This document discusses flow through pipes, including:
- Laminar and turbulent flow characteristics defined by Reynolds number
- Head losses calculated using Darcy-Weisbach and minor loss equations
- Friction factors determined from Moody diagrams for laminar and turbulent flows
- Total head loss in a pipe system equals major losses in pipe sections plus minor losses from fittings
This document discusses energy losses that occur in hydraulic systems. It begins by defining laminar and turbulent flows, and introduces the Reynolds number which determines the type of flow. It then explains that greater energy losses occur in turbulent flow compared to laminar flow. The document goes on to describe the Darcy-Weisbach equation for calculating head losses due to friction in pipes. Specific equations are provided to calculate losses for laminar and turbulent flow, taking into account factors like pipe roughness and Reynolds number. The purpose is to analyze energy losses that occur in components like valves and fittings so they can be properly accounted for in system design.
120218 chapter 8 momentum analysis of flowBinu Karki
The document discusses momentum analysis of fluid flow. It contains the following key points:
1) The momentum equation is based on the law of conservation of momentum, which states that the net force acting on a fluid mass is equal to the rate of change of momentum of the fluid.
2) The momentum principle can be written as an impulse-momentum equation: the impulse of a force acting on a fluid mass over a short time interval is equal to the change in momentum of the fluid.
3) The momentum equation is used to determine the resultant force exerted by a flowing fluid on a pipe bend based on the fluid's velocity, pressure, area, and external forces at two sections of the pipe.
Overview of the Vortex Flow Meter product range from Badger Meter including technical data. This presentation also explains vortex shedding technology.
This document discusses pipe friction and flow experiments. It defines key terms like friction factor, Reynolds number, laminar and turbulent flow. The objective is to use a Moody diagram to determine these variables and the relative roughness of a pipe. Sample calculations are shown for one data point. The methodology involves using the Darcy-Weisbach equation and Moody diagram. Potential errors include human errors in measurement and recording. The conclusion is that all flows studied were turbulent based on their high Reynolds numbers, and that friction factors decrease while head losses increase with higher densities and velocities.
Energy generation from vortex induced vibrations reporteor20104
This document discusses energy generation from vortex induced vibrations of bluff bodies in fluid flows. It describes how vortices form behind bluff bodies at certain flow speeds, creating periodic lift forces that can induce structural vibration. This vibration can be harnessed to extract energy through mechanisms attached to vibrating structures. Specifically, at certain flow speeds vortex shedding frequency locks in with the structure's natural frequency, amplifying vibrations and making more energy available for harvesting. The document provides theoretical background on vortex formation, shedding frequency, lock-in phenomena, and the effect of boundary gaps near structures.
IRJET- Tall-Building Structure Shape Optimization using “Computational Fluid ...IRJET Journal
This document discusses using computational fluid dynamics (CFD) to optimize the shape of tall buildings to reduce wind pressure. It begins by introducing CFD simulation as a suitable method for analyzing how wind pressure is affected by different building shapes. The document then provides background on wind forces on tall buildings and how wind flow patterns are complex. It describes using the realizable k-ε turbulent model in ANSYS software to simulate turbulent wind flow for the CFD analysis. The summary analyzes different building shapes using CFD to select a shape with reduced wind pressure.
Nwtc seminar overview of the impact of turbulence on turbine dynamics and t...ndkelley
Overview of the impact of atmospheric turbulence on wind turbine dynamics and its simulation based on 20 years of research at the National Renewable Energy Laboratory
Vertical construction of skyscrapers is increasing to accommodate growing urban populations within limited space. Structural design of tall buildings must consider both vertical and lateral loads like wind and seismic loads. Wind causes fluctuating forces that depend on factors like wind speed and direction, building geometry, and natural vibration frequencies. Resonance can occur if the vortex shedding frequency matches natural frequencies, requiring mitigation strategies like changing the cross-section. Tall building design must also ensure occupant comfort by limiting vibrations and accelerations from wind loads.
CFD BASED ANALYSIS OF VORTEX SHEDDING IN NEAR WAKE OF HEXAGONAL CYLINDERIRJET Journal
This document presents a computational fluid dynamics (CFD) analysis of vortex shedding in the near wake of a hexagonal cylinder. The study examines the effects of Reynolds number on lift, drag, vortex shedding frequency, and Strouhal number. CFD simulations were performed for Reynolds numbers of 100, 500, and 1000. Results showed increases in drag and lift coefficients with increasing Reynolds number. Velocity contours and pressure contours indicated transition to turbulence in the wake with higher Reynolds numbers. Strouhal number and vortex shedding frequency both increased significantly with Reynolds number. The study provides insight into vortex behavior behind hexagonal cylinders under varying flow conditions.
Cavitation in Francis turbines negatively impacts performance and causes damage. It occurs when pressure drops below vapor pressure, forming bubbles that collapse upon reaching higher pressure zones. This results in pitting on turbine surfaces from high localized pressures. Remedies include optimizing hydraulic design to reduce cavitation, and developing coatings for wetted parts to prolong maintenance intervals. Cavitation repair involves welding or spraying metallic/non-metallic coatings, with some coatings showing better erosion resistance than stainless steel. Preventing cavitation requires correct turbine design, manufacturing quality, material selection, installation, operation, maintenance, and supplemental air injection into the draft tube.
The document discusses vibration damping and Aeolian vibration in overhead power lines. It provides information on different types of wind-induced oscillations like Aeolian vibration, gallop, and simple swinging. It explains the concepts of bluff bodies, vortex shedding, Reynolds number, and their relationship to Aeolian vibration. Finally, it describes different types of vibration dampers used to control Aeolian vibration in conductors, including Stockbridge dampers, spiral vibration dampers, and tuned mass dampers.
Wind induced oscillations
Aeolian vibration
Gallop
Simple swinging
Types of bodies
Bluff/blunt bodies
Vortex shedding
Reasons for vortex shedding
Governing equation
The Reynolds number
Relationship with the Reynolds number
What is Aeolian vibration?
Effect of Aeolian vibration
Working of vibration damper
Stock bridge damper
Spiral vibration damper
Tuned mass damper
Working principle
Effects of Leading-edge Tubercles and Dimples on a Cambered Airfoil and its P...IRJET Journal
This study uses computational fluid dynamics (CFD) to analyze the effects of adding leading-edge tubercles and dimples to a cambered airfoil on its aerodynamic performance. Tubercles and dimples are known to delay boundary layer separation and reduce pressure drag based on observations of humpback whale fins and golf ball dimples. The Wortmann FX 60-126 airfoil is modified with tubercles of varying wavelengths and amplitudes, and dimples are added at the points of boundary layer separation. CFD simulations are run at Reynolds number 120,000 and angles of attack from 0-20 degrees. Preliminary results show the wing with 50mm wavelength and 10mm amplitude
IRJET- Study of Fluid Induced Vibrations using Simulation Means and their Eff...IRJET Journal
This document summarizes research on fluid-induced vibrations in pipes during internal flows. It discusses how turbulent and unsteady flows containing mixtures of water and soil can induce vibrations in dredging pipes and cause abrasion at bends and branches. Computational fluid dynamics (CFD) techniques are used to numerically analyze typical pipe lines and supporter designs under different flow conditions. The research also examines how pressure pulsations from flows can excite pipe vibrations at resonant frequencies, and studies fluid-structure interaction (FSI) phenomena between internal flows and vibrating pipes.
offshore structural design description, starts from codes and standards, data requirements, plate form data, extreme storm parameters, operational parameters and installation parameters
IRJET- A Review of Seismic Analysis of Different Shape of RC Building by usin...IRJET Journal
This document reviews research on seismic analysis of reinforced concrete (RC) buildings using viscous dampers. It summarizes 6 research papers that analyzed the effects of viscous dampers on RC buildings. The main findings are:
1) Viscous dampers reduce displacement, drift, acceleration, and velocity responses in RC buildings compared to buildings without dampers. Dampers placed at lower floors provide better seismic performance.
2) Dampers can reduce displacement by up to 85% and drift by up to 78% compared to bare frames without dampers.
3) Dampers placed at lower floors are most effective at reducing displacement, drift, and increasing the time period of the structure compared to damp
ADEQUACY OF BELT-TRUSS AND OUTRIGGER SYSTEMS WITH VISCOUS DAMPER IN 3D RC FRA...IRJET Journal
This document presents a study on the effectiveness of belt-truss systems, outrigger systems, and viscous dampers in improving the seismic performance of 3D reinforced concrete frames. Twelve models of a G+23 storey reinforced concrete frame are analyzed using finite element modal, equivalent static, and response spectrum analyses. The results in terms of time period, base shear, storey displacement, and storey drift are obtained and discussed. It is found that the models with viscous dampers and belt-trusses/outriggers at multiple locations have lower time periods, base shear, displacements, and drifts compared to the bare frame, indicating improved seismic performance.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
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Fluid Structural Modal Coupled Numerical Investigation of Transonic Flutterin...IJERA Editor
Flutter is an unstable oscillation which can lead to destruction. Flutter can occur on fixed surfaces, such as blades, wing or the stabilizer. By self-excited aeroelastic instability, flutter can lead to mechanical or structural failure of aircraft engine blades. The modern engines have been designed with increased pressure ratio and reduced weight in order to improve aerodynamic efficiency, resulting in severe aeroelastic problems. Particularly flutter in axial compressors with transonic flow can be characterized by a number of aerodynamic nonlinear effects such as shock boundary layer interaction, rotating stall, and tip vortex instability. Rotating blades operating under high centrifugal forces may also encounter structural nonlinearities due to friction damping and large deformations. In the future work a standard axial flow compressor blade will be taken for analysis, both Subsonic and Transonic range are taken for analysis. Fluid and Structure are two different domains which will be coupled by full system coupling technique to predict the fluttering effect on the compressor blade. ANSYS is a commercial simulation tool, which will be deployed in this work to perform FSI (Fluid Structure Interaction) and FSI coupled Modal to predict the flutter in the compressor blades
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2) Mounting vented cylinders on a flat plate and varying the angle of attack, lift coefficients increased with small drag coefficient variations.
3) Moving the vented cylinder further from the leading edge of the flat plate allowed more boundary layer development
1. Study of Column Vibration
MBO Assignment
Prepared By: - Anup kumar Singh
11/5/2015
2. Page 2 of 7
Item
No.
Table of Contents
1 Introduction
2 What is vortex shedding
3 Definitions of Important terms in Vortex Shedding analysis
4 Why does Vortex Shedding Matter
5 Probability of occurrence & requirement of vibration analysis
6 How to Calculate Vortex Shedding
7 Conclusion
8 References
3. Page 3 of 7
Introduction:-
This study is primarily concerned with the vibration of vertical pressure vessels known as columns or towers.
We will discuss following topics related to vortex shedding:
What is vortex shedding
Definitions of Important Terms
Why does vortex shedding matter
Probability of occurrence & requirement of vibration analysis
How to calculate vortex shedding
What is vortex shedding:
Vortex shedding happens when wind hits a structure, causing alternating vortices to form at a certain
frequency. This in turn causes the system to excite and produce a vibrational load. Historically, it has been
very difficult to calculate by hand. Today, with modern technology and new engineering practices, vortex
shedding analysis is a valuable tool used in the design of tall equipment and structures.
If we are designing a tall, slender, structure and it is subject to wind, we need to consider vortex shedding
Vortex Shedding is the instance where alternating low pressure zones (blue colors in figure below) are
generated on the downwind side of the column, as shown in the figure below which showing vortex shedding
phenomenon induced by wind flowing over a cylindrical column.
These alternating low pressure zones cause the column to move towards the low pressure zone, causing
movement perpendicular to the direction of the wind. When the critical wind speed of the column is reached,
these forces can cause the column to resonate where large forces and deflections are experienced. Vortex
shedding is a complex physical phenomenon, especially when it degenerates into lock-in condition. As large
vibrations may occur at moderate and frequent wind velocities, structures may undergo a great number of
stress cycles that lead to damage accumulation and may determine structural failure without exceeding the
ultimate limit stress. Considering the potential vortex shedding fatigue induced damage it is very important
the design procedures to account in a realistic manner for the vortex shedding dynamic induced loads.
Definitions of Important terms in Vortex Shedding analysis:-
Critical wind velocity (Vc): The velocity at which the frequency of vortex shedding matches one of
the normal modes of vibration
4. Page 4 of 7
Logarithmic decrement (δ): Logarithmic decrement is the log of the ratio of successive amplitudes of
damped, freely vibrating structure and is a measure of the structural ability of the stake or tower to
dissipate energy during vibration. For a particular structure δ depends on the type of construction and
lining used.
Static deflection: Deflection due to wind or earthquake in the direction of load.
Dynamic deflection:Deflection due to vortex shedding perpendicular to the direction of the wind.
Lock-in: A cylinder is said to be “locked in” when the frequency of oscillation is equal to the
frequency of vortex shedding. In this region the largest amplitude oscillations occur.
Why does Vortex Shedding Matter:
The frequency of the vortices is dependent on the shape of the body, and the velocity of the fluid flow or wind
hitting this body. The vortices create low pressure zones on the downwind side of the object on alternate sides.
As the fluid flows to fill the low pressure zone, it produces a vibration at a specific calculable frequency. This
vibration is only a major concern if it happens to coincide with the natural frequency of the structure.
The wind velocity at which the frequency of vortex shedding matches the natural period of vibration is called
the critical wind velocity. Wind-induced oscillations occur at steady, moderate wind velocities of 20-25 miles
per hour. These oscillations commence as the frequency of vortex shedding approaches the natural period of
the stack or column and are perpendicular to the prevailing wind. Larger wind velocities contain high velocity
random gusts that reduce the tendency for vortex shedding in a regular periodic manner.
For structures that are tall and uniform in size and shape, the vibrations can be damaging and ultimately lead
to fatigue failure. Towers/Columns are highly susceptible to vibrations induced by vortex shedding. By
completing a vortex shedding analysis of structures under wind loading, we can evaluate whether more
efficient structures can and should be developed.
Probability of occurrence & requirement of vibration analysis:
Once a vessel has been designed statically, it is necessary to determine if the vessel is susceptible to wind-
induced vibration. Historically, the thumb rule was to do a dynamic wind check only if the vessel L/D ratio
exceeded 15 and the POV (Period of Vibration) was greater than 0.4 seconds. This criterion has proven to be
unconservative for a number of applications. In addition, if the critical wind velocity, Vc, is greater than 50
mph, then no further investigation is required. Wind speeds in excess of 50mph always contain gusts that will
disrupt uniform vortex shedding.
The above mentioned criteria may give first impression regarding stability of structure under vortex shedding,
but to ensure with more certainty structure shall be checked with following criterion:
Criterion 1
If W/LDr2 < 20, a vibration analysis must be performed
If 20< W/LDr2 < 25, a vibration analysis should be performed
If W/LDr2 > 25, a vibration analysis need not be performed
Criterion 2
If Wδ/LDr2 < 0.75, the vessel is unstable.
If 0.75 < Wδ/LDr2 < 0.95, the vessel is probably unstable.
If Wδ/LDr2 > 0.95, the vessel is stable
5. Page 5 of 7
Limitations of the above criterion are that it should be restricted to cylindrical steel cantilevered structures
having fairly uniform distribution of non-stiffness masses and width Lc /L ratios less than 0.5, (D/L2) (10)4
less than eight, W/Ws ratio not exceeding six.
Where;
W :- Total weight of structure in lb
Ws :- Weight of structure excluding weight of parts which do not contribute to stiffness, lb
L :- Total length of structure, ft
Lc:- Total length of conical sections of structure, ft
D :- Average internal diameter of structure, ft
Dr: - Average internal diameter of top half of structure, ft
δ: - Logarithmic decrement
WF = Wδ/LDr2:- Damping factor
How to Calculate Vortex Shedding:-
Step 1: Determine the Vortex shedding Frequency
The vortex street frequency is calculated using the Reynolds number (which describes the fluid flow
characteristics) and the Strouhal number (which describes the oscillations of a fluid). The Reynolds number is
calculated using viscosity, density, flow velocity, and some geometry from the object in the fluid. It is
calculated over a range of flow speeds (or wind velocities). The Strouhal number is then calculated from those
Reynolds numbers, although for laminar flow situations a Strouhal of 0.2 is often used. The frequency of the
vortex street is then calculated using the Strouhal number, the width of the body, and the flow speed.
Re = VD /ν
Where:
Re = Reynolds number;
V= wind speed [m/s];
D= Structure diameter [m];
ν = kinematic viscosity [m2
/s].
Fluid characteristics’ in Reynolds number:-
Sub critical Range: Re < 3x105
Critical Range: 3x105 ≤ Re ≤ 3x106
Trans critical Range: Re > 3x106
Strouhal number:-
Subcritical (Re < 3x105): 0.18 (for circular cross section)
Supercritical and Trans critical (Re > 3x105): 0.25 (for circular cross section)
Vortex Shedding Frequency:-
fs = SV/ D
Where
fs = Vortex shedding frequency
S= Strouhal number
D= Structure diameter
6. Page 6 of 7
Step 2: Find the natural frequencies of the mechanical system
For the complex geometry of columns with the varying diameters, thickness and materials. In the past, finding
the correct mathematical model of such a structure in order to find the natural frequency would be difficult
and inaccurate. Today, with the advancement of technology and engineering practice, calculating the natural
frequency can be done fairly efficiently. Finite Element Analysis software such as Solid Works’ Simulation
Package can be used to calculate the natural frequency of a very complex system.
Step 3: Comparing Natural frequencies to calculated frequencies
Now that we have the natural frequencies of the mechanical system, we can compare these frequencies to the
vortex shedding frequencies as calculated in step 1. If the natural frequency line up to the vortex shedding
frequencies calculated in stage 1 and the wind speed scenarios, it is highly likely column could have a
problem for its stability. It is important to apply sound engineering judgment at this stage when interpreting
the results. The formulas used in this calculation are only good for a certain rage of wind speeds and to some
degree are based on experimental data. The accuracy of the analysis also depends on how accurate of a model
is used for analysis. There are several steps we can take in order to prevent vortex shedding.
Step 4: Fixing the problem
There are three main approaches that can be applied to prevent the structural failure from vortex shedding.
The simplest is to address the fluid flow and create a disturbance on the structure so that the vortex street
cannot form. This is commonly done by adding a spiral at the top of the structure (but any change to the body
that disrupts the vortex would work). Another method is to design the structure itself so the natural
frequencies are outside the operating frequencies. This can be done by varying the cross-section along the
length of the structure or by adding or changing supports. There are also dynamic systems such as dampeners
that can successfully be applied to absorb vibration.
While vortex shedding is a common phenomenon that can lead to structural failure, it is one that is often
overlooked because of the complexity of modeling the situation correctly. Using the steps outlined above,
vibrational problems can be easily identified and a few hypotheses can be tested. Design changes can be made
before any real problem arises. The key point to remember is if we are designing a tall slender mechanical
system exposed to wind loading, make sure that we are considering vortex shedding vibrations and conducts
the appropriate analysis.
The following design modifications may be made to the vessel to eliminate vortex shedding:
Add thickness to bottom shell courses and skirt to increase damping and raise the POV.
Reduce the top diameter where possible.
For stacks, add helical strakes to the top third of the stack only as a last resort. Spoilers or strakes
should protrude beyond the stack diameter by a distance of d/12 but not less than 2 in.
Cross-brace vessels together.
Add guy cables or wires to grade.
Add internal linings.
Reduce vessel below dynamic criteria.
The following precautions should be taken for structure susceptible for Vortex Shedding:-
Include ladders, platforms, and piping in your calculations to more accurately determines the natural
frequency.
Grout the vessel base as soon as possible after erection while it is most susceptible to wind vibration.
Add external attachments as soon as possible after erection to break up vortices.
Ensure that tower anchor bolts are tightened as soon as possible after erection.
7. Page 7 of 7
CONCLUSION:-
The design method to be used for vertical pressure vessels depends on whether the longitudinal stress in the
shell is tension or compression, and on whether the vessel is subjected to internal or external pressure. Self-
supporting vertical pressure vessels should always be investigated regarding their possible behavior under
vibrating conditions. The evaluation of wind velocity effects should include considerations pertaining to the
distribution of external vessel attachments as well as the surrounding equipment and terrain. It should be
borne in mind that liquid loading in vessels having trays will help dampen vibration, but should not be relied
upon as a cure all. If vibration trouble does occur, careful analysis of any proposed remedy must be made in
order to avoid trouble from some other source. External loads applied to vertical pressure vessels produce
axial loading and bending moments on the vessel. These result in axial tensions and compressions in the shell,
which must be combined with the effects of the pressure loading to give the total longitudinal stress acting in
the shell.
REFERENCES:-
Lecture: Prof. A. H. Techet
International Journal of Mechanical Engineering and Technology (IJMET), ISSN
Structural Vortex Shedding Response Estimation Methodology and Finite Element Simulation:
I. Giosan, P.Eng.
PVD Manual: Dennis Moss