This document discusses various mathematical models for traffic flow analysis. It begins by introducing Greenshield's linear speed-density model from 1935 as the first macroscopic traffic flow model. It then discusses limitations of this model and introduces other models like Greenberg's logarithmic model and Underwood's exponential model. The document also discusses Pipe's generalized model that can produce different models by varying a parameter. Finally, it introduces the concept of multi-regime models that use different speed-density relationships for congested and uncongested traffic conditions.
Pergamon Transpn. Res.-B. Vol. 28B, No. 4, pp. 269-287, 19.docxkarlhennesey
Pergamon
Transpn. Res.-B. Vol. 28B, No. 4, pp. 269-287, 1994
Copyright 0 1994 Elsevier Science Ltd
Printed in the UK. All rights reserved
0191-2615194 $6.00 + .OO
0191-2615(93)E0002-3
THE CELL TRANSMISSION MODEL: A DYNAMIC
REPRESENTATION OF HIGHWAY TRAFFIC
CONSISTENT WITH THE HYDRODYNAMIC THEORY
CARLOS F. DAGANZO
Department of Civil Engineering and Institute of Transportation Studies,
University of California, Berkeley CA 94720, U.S.A.
(Received 23 October 1992; in revisedform 13 July 1993)
Abstract-This paper presents a simple representation of traffic on a highway with a single
entrance and exit. The representation can be used to predict traffic’s evolution over time and
space, including transient phenomena such as the building, propagation, and dissipation of
queues. The easy-to-solve difference equations used to predict traffic’s evolution are shown to be
the discrete analog of the differential equations arising from a special case of the hydrodynamic
model of traffic flow. The proposed method automatically generates appropriate changes in
density at locations where the hydrodynamic theory would call for a shockwave; i.e., a jump in
density such as those typically seen at the end of every queue. The complex side calculations
required by classical methods to keep track of shockwaves are thus eliminated. The paper also
shows how the equations can mimic the real-life development of stop-and-go traffic within moving
queues.
1. INTRODUCTION
Accurate descriptions of highway traffic flow over transportation networks, whether at
the planning or operations level, must recognize that the vehicles traveling on any section
of the network must be bound for specific destinations.
Static traffic assignment models used for transportation planning (see Sheffi, 1985,
for example) achieve this goal by describing the flow on a link of the network by its
components by final destination; e.g., by specifying a variable yid that represents the
amount of flow on link i that is ultimately bound for destination d. Unfortunately, this is
much more difficult to do for dynamic network flow problems (with time-dependent
origin-destination (O-D) flows) because the functional dependence of the link flows at
time t, yid(f), on the collection of all past flows is quite complex. This problem manifests
itself both at the planning level, where networks are quite complex, and at the operations
level, where networks are simpler, but more detail is sought about the system’s evolution.
Although dynamic traffic assignment models -planning level models involving large
networks- typically recognize that traffic travels to many destinations, the models are
based on simplistic flow relationships that are not perfectly consistent with the conserva-
tion laws of traffic. A planned sequel to this paper will discuss this in more detail.
Traffic operations models can be microscopic or macroscopic. Microscopic simula-
tions (e.g., Schw ...
The document reviews optimal speed car-following models. It discusses macroscopic and microscopic traffic models, with a focus on microscopic optimal speed models. The optimal speed model defines a desired speed that is a function of headway distance and helps model traffic flow situations. The document also proposes enhancements to the optimal speed model, including a weighting factor dependent on relative speed and spacing to improve braking reactivity. In conclusion, it evaluates optimal speed models and their ability to realistically model traffic dynamics while avoiding collisions.
Adjusting the flow in crucial areas can maximize the overall throughput of traffic along a stretch of road. This is of particular interest in regions of high traffic density, which may be caused by high volume peak time traffic, accidents or closure of one or more lanes of the road.
The document discusses traffic stream models. It describes two classes of traffic models: macroscopic models that examine average behaviors like density and speed, and microscopic models that examine individual behaviors like car-following models. The car-following model assumes cars cannot pass and a car's acceleration depends on the headway distance and speed difference of the car in front. Conservation laws state that the number of cars in a highway segment remains constant over time. Greenshield's model relates traffic speed to density, with free flow at low density and zero speed at maximum density. The document outlines concepts like flow rate, spacing, headway, density and speed-flow-density relationships.
A Model For The Dynamic System Optimum Traffic Assignment ProblemSean Flores
This document describes a model for the dynamic system optimum traffic assignment problem. The model seeks to reduce total travel delays in a road network by routing drivers along routes with the lowest marginal delay. It is applicable to networks with many origin-destination pairs and bottlenecks. The model discretizes time and simulates vehicle movement to determine link flows and queues while respecting the first-in, first-out queue discipline at bottlenecks. Numerical results are provided for two test networks to demonstrate the model.
This document provides a review of fuzzy microscopic traffic flow models. It discusses how fuzzy logic can be used to model traffic flow and driver behavior by introducing uncertainty into variables like speed and headway. It describes fuzzy cellular automata models that represent traffic as vehicles characterized by fuzzy numbers for position and velocity. It also covers fuzzy logic car-following models that use linguistic terms and rules to model car-following behavior, and fuzzy route choice models that calculate possibility indexes to determine the most likely route. The goal of these fuzzy models is to more realistically simulate traffic flow and account for the imprecise nature of traffic data.
This document provides an overview of a student's assignment reviewing fuzzy microscopic traffic flow models. It discusses how fuzzy logic can be used to introduce uncertainty into traffic simulation models to better reflect real-world conditions. It reviews different types of fuzzy microscopic models, including fuzzy cellular models that use fuzzy numbers to represent vehicle parameters and transitions between time steps, and fuzzy logic car-following models that use fuzzy reasoning and linguistic terms to describe driver behavior. The goal is to understand how these fuzzy microscopic models work.
A Biologically Inspired Network Design ModelXin-She Yang
This document summarizes a biologically inspired network design model based on the foraging behavior of the slime mold Physarum polycephalum. The model uses a gravity model to estimate traffic flows between cities and simulates the slime mold's development of a protoplasmic network to connect food sources. It applies this approach to design transportation networks for Mexico and China, comparing the results to existing networks. The networks are evaluated based on cost, efficiency, and robustness. The model converges to solutions that balance these factors in a flexible and optimized way inspired by biological networks.
Pergamon Transpn. Res.-B. Vol. 28B, No. 4, pp. 269-287, 19.docxkarlhennesey
Pergamon
Transpn. Res.-B. Vol. 28B, No. 4, pp. 269-287, 1994
Copyright 0 1994 Elsevier Science Ltd
Printed in the UK. All rights reserved
0191-2615194 $6.00 + .OO
0191-2615(93)E0002-3
THE CELL TRANSMISSION MODEL: A DYNAMIC
REPRESENTATION OF HIGHWAY TRAFFIC
CONSISTENT WITH THE HYDRODYNAMIC THEORY
CARLOS F. DAGANZO
Department of Civil Engineering and Institute of Transportation Studies,
University of California, Berkeley CA 94720, U.S.A.
(Received 23 October 1992; in revisedform 13 July 1993)
Abstract-This paper presents a simple representation of traffic on a highway with a single
entrance and exit. The representation can be used to predict traffic’s evolution over time and
space, including transient phenomena such as the building, propagation, and dissipation of
queues. The easy-to-solve difference equations used to predict traffic’s evolution are shown to be
the discrete analog of the differential equations arising from a special case of the hydrodynamic
model of traffic flow. The proposed method automatically generates appropriate changes in
density at locations where the hydrodynamic theory would call for a shockwave; i.e., a jump in
density such as those typically seen at the end of every queue. The complex side calculations
required by classical methods to keep track of shockwaves are thus eliminated. The paper also
shows how the equations can mimic the real-life development of stop-and-go traffic within moving
queues.
1. INTRODUCTION
Accurate descriptions of highway traffic flow over transportation networks, whether at
the planning or operations level, must recognize that the vehicles traveling on any section
of the network must be bound for specific destinations.
Static traffic assignment models used for transportation planning (see Sheffi, 1985,
for example) achieve this goal by describing the flow on a link of the network by its
components by final destination; e.g., by specifying a variable yid that represents the
amount of flow on link i that is ultimately bound for destination d. Unfortunately, this is
much more difficult to do for dynamic network flow problems (with time-dependent
origin-destination (O-D) flows) because the functional dependence of the link flows at
time t, yid(f), on the collection of all past flows is quite complex. This problem manifests
itself both at the planning level, where networks are quite complex, and at the operations
level, where networks are simpler, but more detail is sought about the system’s evolution.
Although dynamic traffic assignment models -planning level models involving large
networks- typically recognize that traffic travels to many destinations, the models are
based on simplistic flow relationships that are not perfectly consistent with the conserva-
tion laws of traffic. A planned sequel to this paper will discuss this in more detail.
Traffic operations models can be microscopic or macroscopic. Microscopic simula-
tions (e.g., Schw ...
The document reviews optimal speed car-following models. It discusses macroscopic and microscopic traffic models, with a focus on microscopic optimal speed models. The optimal speed model defines a desired speed that is a function of headway distance and helps model traffic flow situations. The document also proposes enhancements to the optimal speed model, including a weighting factor dependent on relative speed and spacing to improve braking reactivity. In conclusion, it evaluates optimal speed models and their ability to realistically model traffic dynamics while avoiding collisions.
Adjusting the flow in crucial areas can maximize the overall throughput of traffic along a stretch of road. This is of particular interest in regions of high traffic density, which may be caused by high volume peak time traffic, accidents or closure of one or more lanes of the road.
The document discusses traffic stream models. It describes two classes of traffic models: macroscopic models that examine average behaviors like density and speed, and microscopic models that examine individual behaviors like car-following models. The car-following model assumes cars cannot pass and a car's acceleration depends on the headway distance and speed difference of the car in front. Conservation laws state that the number of cars in a highway segment remains constant over time. Greenshield's model relates traffic speed to density, with free flow at low density and zero speed at maximum density. The document outlines concepts like flow rate, spacing, headway, density and speed-flow-density relationships.
A Model For The Dynamic System Optimum Traffic Assignment ProblemSean Flores
This document describes a model for the dynamic system optimum traffic assignment problem. The model seeks to reduce total travel delays in a road network by routing drivers along routes with the lowest marginal delay. It is applicable to networks with many origin-destination pairs and bottlenecks. The model discretizes time and simulates vehicle movement to determine link flows and queues while respecting the first-in, first-out queue discipline at bottlenecks. Numerical results are provided for two test networks to demonstrate the model.
This document provides a review of fuzzy microscopic traffic flow models. It discusses how fuzzy logic can be used to model traffic flow and driver behavior by introducing uncertainty into variables like speed and headway. It describes fuzzy cellular automata models that represent traffic as vehicles characterized by fuzzy numbers for position and velocity. It also covers fuzzy logic car-following models that use linguistic terms and rules to model car-following behavior, and fuzzy route choice models that calculate possibility indexes to determine the most likely route. The goal of these fuzzy models is to more realistically simulate traffic flow and account for the imprecise nature of traffic data.
This document provides an overview of a student's assignment reviewing fuzzy microscopic traffic flow models. It discusses how fuzzy logic can be used to introduce uncertainty into traffic simulation models to better reflect real-world conditions. It reviews different types of fuzzy microscopic models, including fuzzy cellular models that use fuzzy numbers to represent vehicle parameters and transitions between time steps, and fuzzy logic car-following models that use fuzzy reasoning and linguistic terms to describe driver behavior. The goal is to understand how these fuzzy microscopic models work.
A Biologically Inspired Network Design ModelXin-She Yang
This document summarizes a biologically inspired network design model based on the foraging behavior of the slime mold Physarum polycephalum. The model uses a gravity model to estimate traffic flows between cities and simulates the slime mold's development of a protoplasmic network to connect food sources. It applies this approach to design transportation networks for Mexico and China, comparing the results to existing networks. The networks are evaluated based on cost, efficiency, and robustness. The model converges to solutions that balance these factors in a flexible and optimized way inspired by biological networks.
A Biologically Inspired Network Design ModelXin-She Yang
This document summarizes a biologically inspired network design model based on the foraging behavior of the slime mold Physarum polycephalum. The model uses a gravity model to estimate traffic flows between cities and simulates the slime mold's development of a protoplasmic network to connect food sources. It applies this approach to design transportation networks for Mexico and China, comparing the results to existing networks. The networks are evaluated based on cost, efficiency, and robustness. The model converges to solutions that balance these factors in a flexible and optimized way inspired by biological networks.
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 summarizes a computational fluid dynamics (CFD) simulation of flow over an Ahmed body using Reynolds-averaged Navier-Stokes (RANS) turbulence modelling. Three grids with different refinements were used. The Realizable k-epsilon turbulence model was chosen. The simulation results showed improved prediction of drag coefficient with finer grids but poorer prediction of velocity profiles compared to experimental data. Flow analysis identified two main vortices in the wake, with higher turbulence kinetic energy around the lower vortex, consistent with experiments.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
This document summarizes a numerical study on free-surface flow conducted using a computational fluid dynamics (CFD) solver. The study examines the wave profile generated by a submerged hydrofoil through several test cases varying parameters like the turbulence model, grid resolution, and hydrofoil depth. The document provides background on the governing equations solved by the CFD solver and the interface capturing technique used to model the free surface. Five test cases are described that investigate grid convergence, the impact of laminar vs turbulent models, the relationship between hydrofoil depth and wave height, and the effect of discretization schemes.
This document provides a review and analysis of the optimal speed model. It discusses:
1) The theoretical models that support the optimal speed model including microscopic, mesoscopic, and macroscopic traffic flow models.
2) Problems with the original optimal speed model including unrealistic behavior, instability, and stop-and-go waves.
3) A proposed double boundary optimal velocity function model that allows vehicles to operate within a range of speeds and spacings rather than at a single optimal point. This addresses issues with the original model.
This document discusses using statistical learning techniques and direct numerical simulation (DNS) data to develop closure relationships for a simplified two-fluid model of bubbly two-phase flow in a vertical channel. DNS is used to simulate bubbly upflow in the channel, and the data is averaged and used to train a neural network model to relate unknown closure terms in the two-fluid model equations to resolved variables. The model predictions are then tested against additional DNS data. The presence of walls adds complexity compared to previous work on periodic domains by introducing new closure terms related to surface tension effects near walls.
A Cell-Based Variational Inequality Formulation Of The Dynamic User Optimal A...Joe Osborn
This summarizes a research paper that develops a cell-based dynamic traffic assignment formulation using a variational inequality approach. The formulation encapsulates the Cell Transmission Model to capture traffic dynamics like shockwaves and queues. It aims to precisely follow the ideal dynamic user optimal principle where all used routes between an origin-destination pair have equal travel times. An alternating direction method is used to solve the variational inequality problem. The paper evaluates the formulation using two scenarios to demonstrate traffic dynamics, interactions across links, and adherence to the dynamic user optimal principle.
This document reviews several extensions and applications of the optimal speed traffic model. The original optimal speed model introduced in 1995 assumes that each vehicle has a legal velocity that depends on the following distance. Later models like the generalized force model and full velocity difference model address issues like unrealistic acceleration and deceleration in the original model. Other extensions examine the effects of next-nearest neighbor interaction and backward-looking behavior. Applications of optimal speed models include autonomous vehicle control, evaluating ITS strategies, and gaining insights into traffic congestion formation and flow stability. The conclusion recommends developing a more systematic "almighty model" that incorporates the various extensions and applications.
This document summarizes a study using Star-CCM+ software to model microfluidic flows. Single-phase flow in rectangular and circular microchannels was modeled and validated against analytical solutions. Droplet formation in a microfluidic T-junction and flow focusing device was also modeled using the volume of fluid method. High spurious currents were observed at fluid interfaces with coarse meshes. Adaptive mesh refinement was employed for the flow focusing device to minimize currents and sharpen interfaces, improving the model.
This document discusses fundamentals of traffic flow and queuing theory. It defines traffic flow parameters for uninterrupted and interrupted traffic streams. It describes traffic flow, speed, and density measurements including volume, time headway, average and space mean speed, and density. It presents speed-density, flow-density, and speed-flow models and discusses macroscopic and microscopic traffic flow approaches. It also introduces Greenshields and Greenberg traffic flow models and how to calibrate macroscopic models using linear regression analysis.
The document reviews optimal speed traffic flow models. It discusses macroscopic and microscopic models, with a focus on car-following models and the optimal velocity model (OVM). The OVM describes how each vehicle tries to travel at an optimal speed based on the distance to the preceding vehicle. Several improved models are presented, including the comprehensive optimal velocity model which considers both distance and speed difference, and the optimal velocity forecast model which incorporates anticipated speed changes. While the models reviewed consider single-lane traffic, the conclusion recommends including non-car vehicles and driver behaviors more common to Nigeria for greater applicability.
Determination of shock losses and pressure losses in ug mine openingsSafdar Ali
This document discusses determining pressure and shock losses in underground mine openings using computational fluid dynamics (CFD) simulation techniques. It aims to calculate losses in different mine configurations using CFD and compare results to classical formulas. The document outlines the objective, scope, literature review on losses, and CFD methodology. It describes setting up simulations of common mine geometries like tunnels, bends, junctions, and shafts in Gambit meshing software and analyzing them in Fluent. Results are presented on velocity profiles and pressure losses for configurations like gradual contractions and expansions.
Determination of shock losses and pressure losses in ug mine openings (1)Safdar Ali
This document discusses the determination of shock and pressure losses in underground mine openings using computational fluid dynamics (CFD) simulation techniques. The objective is to calculate losses in different mine configurations and compare results from CFD simulations to classical formulas. The document outlines the scope of the project, literature review on losses, and describes meshing mine geometries in Gambit and performing CFD simulations in Fluent. Results are presented for simulations of tunnels, bends, junctions, contractions, expansions, shafts, and regulators. CFD-generated shock loss coefficients are found to agree reasonably well with published values, except for splits/junctions and forcing shafts, which may be due to modeling limitations. The conclusion is that 3D
Vortex lattice methods are used to estimate aircraft aerodynamics by solving Laplace's equation. They are similar to panel methods in that singularities are placed on a surface and boundary conditions are applied at control points. However, vortex lattice methods are oriented toward lifting surfaces and treat boundary conditions on a mean surface rather than the actual surface. The document outlines the derivation of the thin airfoil boundary condition and pressure relation used in vortex lattice methods through linearization and transfer of the boundary condition to a reference surface. This allows the problem to be treated as a superposition of lift from camber, thickness, and angle of attack.
Macroscopic Traffic Flow model for nepalese roadsHemant Tiwari
This research deals with the calibration of various conventional macroscopic traffic flow models of Nepalese Roads and recommend the best suitable model after undergoing calibration and validation process.
Aerodynamics of 3 d lifting surfaces through vortex lattice methodsMarco Rojas
Vortex lattice methods are similar to panel methods in that they use singularities placed on a surface to satisfy boundary conditions. However, vortex lattice methods are oriented toward lifting effects and ignore thickness. They apply boundary conditions on a mean surface rather than the actual surface. The document provides details on the vortex lattice method, including the linearized boundary condition applied on the mean surface and the thin airfoil pressure relation derived from this. It also describes how the problem can be decomposed into lift, camber, and thickness components using superposition.
The document summarizes numerical simulations of the flow inside a centrifugal compressor's vaneless diffuser and volute. Gambit was used to generate meshes of the geometries, and Fluent was used to simulate the flows. Results from simulations at different speeds and mass flows agreed well with experimental data. The simulations showed separated flow on the diffuser hub wall at low mass flows. Inside the volute, swirling flow structures like vortices were observed. The tongue region caused static pressure distortions that affected the flow.
This document summarizes a study that uses neural networks and direct numerical simulations to develop closure models for two-fluid equations describing multiphase bubbly flows. Direct numerical simulations were performed for a system of bubbles rising in liquid and these results were used to train a neural network model. The neural network model was able to reasonably predict the evolution of different initial bubble distributions and velocities compared to direct numerical simulations. This approach shows promise for using computational simulations to develop reduced-order models that can simulate multiphase flows without resolving all length and time scales.
The document presents a mathematical model for macroscopic traffic flow. It introduces three key variables: traffic flow (q), density (ρ), and speed (v). It uses the conservation principle to relate these variables, stating that the change in the number of cars within a road segment over time is equal to the net flow of cars into and out of that segment. This leads to an equation showing that traffic flow is equal to the product of traffic density and traffic speed. The document lays the groundwork for formulating traffic problems in terms of partial differential equations that can be solved.
A Biologically Inspired Network Design ModelXin-She Yang
This document summarizes a biologically inspired network design model based on the foraging behavior of the slime mold Physarum polycephalum. The model uses a gravity model to estimate traffic flows between cities and simulates the slime mold's development of a protoplasmic network to connect food sources. It applies this approach to design transportation networks for Mexico and China, comparing the results to existing networks. The networks are evaluated based on cost, efficiency, and robustness. The model converges to solutions that balance these factors in a flexible and optimized way inspired by biological networks.
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 summarizes a computational fluid dynamics (CFD) simulation of flow over an Ahmed body using Reynolds-averaged Navier-Stokes (RANS) turbulence modelling. Three grids with different refinements were used. The Realizable k-epsilon turbulence model was chosen. The simulation results showed improved prediction of drag coefficient with finer grids but poorer prediction of velocity profiles compared to experimental data. Flow analysis identified two main vortices in the wake, with higher turbulence kinetic energy around the lower vortex, consistent with experiments.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
This document summarizes a numerical study on free-surface flow conducted using a computational fluid dynamics (CFD) solver. The study examines the wave profile generated by a submerged hydrofoil through several test cases varying parameters like the turbulence model, grid resolution, and hydrofoil depth. The document provides background on the governing equations solved by the CFD solver and the interface capturing technique used to model the free surface. Five test cases are described that investigate grid convergence, the impact of laminar vs turbulent models, the relationship between hydrofoil depth and wave height, and the effect of discretization schemes.
This document provides a review and analysis of the optimal speed model. It discusses:
1) The theoretical models that support the optimal speed model including microscopic, mesoscopic, and macroscopic traffic flow models.
2) Problems with the original optimal speed model including unrealistic behavior, instability, and stop-and-go waves.
3) A proposed double boundary optimal velocity function model that allows vehicles to operate within a range of speeds and spacings rather than at a single optimal point. This addresses issues with the original model.
This document discusses using statistical learning techniques and direct numerical simulation (DNS) data to develop closure relationships for a simplified two-fluid model of bubbly two-phase flow in a vertical channel. DNS is used to simulate bubbly upflow in the channel, and the data is averaged and used to train a neural network model to relate unknown closure terms in the two-fluid model equations to resolved variables. The model predictions are then tested against additional DNS data. The presence of walls adds complexity compared to previous work on periodic domains by introducing new closure terms related to surface tension effects near walls.
A Cell-Based Variational Inequality Formulation Of The Dynamic User Optimal A...Joe Osborn
This summarizes a research paper that develops a cell-based dynamic traffic assignment formulation using a variational inequality approach. The formulation encapsulates the Cell Transmission Model to capture traffic dynamics like shockwaves and queues. It aims to precisely follow the ideal dynamic user optimal principle where all used routes between an origin-destination pair have equal travel times. An alternating direction method is used to solve the variational inequality problem. The paper evaluates the formulation using two scenarios to demonstrate traffic dynamics, interactions across links, and adherence to the dynamic user optimal principle.
This document reviews several extensions and applications of the optimal speed traffic model. The original optimal speed model introduced in 1995 assumes that each vehicle has a legal velocity that depends on the following distance. Later models like the generalized force model and full velocity difference model address issues like unrealistic acceleration and deceleration in the original model. Other extensions examine the effects of next-nearest neighbor interaction and backward-looking behavior. Applications of optimal speed models include autonomous vehicle control, evaluating ITS strategies, and gaining insights into traffic congestion formation and flow stability. The conclusion recommends developing a more systematic "almighty model" that incorporates the various extensions and applications.
This document summarizes a study using Star-CCM+ software to model microfluidic flows. Single-phase flow in rectangular and circular microchannels was modeled and validated against analytical solutions. Droplet formation in a microfluidic T-junction and flow focusing device was also modeled using the volume of fluid method. High spurious currents were observed at fluid interfaces with coarse meshes. Adaptive mesh refinement was employed for the flow focusing device to minimize currents and sharpen interfaces, improving the model.
This document discusses fundamentals of traffic flow and queuing theory. It defines traffic flow parameters for uninterrupted and interrupted traffic streams. It describes traffic flow, speed, and density measurements including volume, time headway, average and space mean speed, and density. It presents speed-density, flow-density, and speed-flow models and discusses macroscopic and microscopic traffic flow approaches. It also introduces Greenshields and Greenberg traffic flow models and how to calibrate macroscopic models using linear regression analysis.
The document reviews optimal speed traffic flow models. It discusses macroscopic and microscopic models, with a focus on car-following models and the optimal velocity model (OVM). The OVM describes how each vehicle tries to travel at an optimal speed based on the distance to the preceding vehicle. Several improved models are presented, including the comprehensive optimal velocity model which considers both distance and speed difference, and the optimal velocity forecast model which incorporates anticipated speed changes. While the models reviewed consider single-lane traffic, the conclusion recommends including non-car vehicles and driver behaviors more common to Nigeria for greater applicability.
Determination of shock losses and pressure losses in ug mine openingsSafdar Ali
This document discusses determining pressure and shock losses in underground mine openings using computational fluid dynamics (CFD) simulation techniques. It aims to calculate losses in different mine configurations using CFD and compare results to classical formulas. The document outlines the objective, scope, literature review on losses, and CFD methodology. It describes setting up simulations of common mine geometries like tunnels, bends, junctions, and shafts in Gambit meshing software and analyzing them in Fluent. Results are presented on velocity profiles and pressure losses for configurations like gradual contractions and expansions.
Determination of shock losses and pressure losses in ug mine openings (1)Safdar Ali
This document discusses the determination of shock and pressure losses in underground mine openings using computational fluid dynamics (CFD) simulation techniques. The objective is to calculate losses in different mine configurations and compare results from CFD simulations to classical formulas. The document outlines the scope of the project, literature review on losses, and describes meshing mine geometries in Gambit and performing CFD simulations in Fluent. Results are presented for simulations of tunnels, bends, junctions, contractions, expansions, shafts, and regulators. CFD-generated shock loss coefficients are found to agree reasonably well with published values, except for splits/junctions and forcing shafts, which may be due to modeling limitations. The conclusion is that 3D
Vortex lattice methods are used to estimate aircraft aerodynamics by solving Laplace's equation. They are similar to panel methods in that singularities are placed on a surface and boundary conditions are applied at control points. However, vortex lattice methods are oriented toward lifting surfaces and treat boundary conditions on a mean surface rather than the actual surface. The document outlines the derivation of the thin airfoil boundary condition and pressure relation used in vortex lattice methods through linearization and transfer of the boundary condition to a reference surface. This allows the problem to be treated as a superposition of lift from camber, thickness, and angle of attack.
Macroscopic Traffic Flow model for nepalese roadsHemant Tiwari
This research deals with the calibration of various conventional macroscopic traffic flow models of Nepalese Roads and recommend the best suitable model after undergoing calibration and validation process.
Aerodynamics of 3 d lifting surfaces through vortex lattice methodsMarco Rojas
Vortex lattice methods are similar to panel methods in that they use singularities placed on a surface to satisfy boundary conditions. However, vortex lattice methods are oriented toward lifting effects and ignore thickness. They apply boundary conditions on a mean surface rather than the actual surface. The document provides details on the vortex lattice method, including the linearized boundary condition applied on the mean surface and the thin airfoil pressure relation derived from this. It also describes how the problem can be decomposed into lift, camber, and thickness components using superposition.
The document summarizes numerical simulations of the flow inside a centrifugal compressor's vaneless diffuser and volute. Gambit was used to generate meshes of the geometries, and Fluent was used to simulate the flows. Results from simulations at different speeds and mass flows agreed well with experimental data. The simulations showed separated flow on the diffuser hub wall at low mass flows. Inside the volute, swirling flow structures like vortices were observed. The tongue region caused static pressure distortions that affected the flow.
This document summarizes a study that uses neural networks and direct numerical simulations to develop closure models for two-fluid equations describing multiphase bubbly flows. Direct numerical simulations were performed for a system of bubbles rising in liquid and these results were used to train a neural network model. The neural network model was able to reasonably predict the evolution of different initial bubble distributions and velocities compared to direct numerical simulations. This approach shows promise for using computational simulations to develop reduced-order models that can simulate multiphase flows without resolving all length and time scales.
The document presents a mathematical model for macroscopic traffic flow. It introduces three key variables: traffic flow (q), density (ρ), and speed (v). It uses the conservation principle to relate these variables, stating that the change in the number of cars within a road segment over time is equal to the net flow of cars into and out of that segment. This leads to an equation showing that traffic flow is equal to the product of traffic density and traffic speed. The document lays the groundwork for formulating traffic problems in terms of partial differential equations that can be solved.
Similar to rekayasa-transportasi-modul-6-modelling.pptx (20)
Harnessing WebAssembly for Real-time Stateless Streaming PipelinesChristina Lin
Traditionally, dealing with real-time data pipelines has involved significant overhead, even for straightforward tasks like data transformation or masking. However, in this talk, we’ll venture into the dynamic realm of WebAssembly (WASM) and discover how it can revolutionize the creation of stateless streaming pipelines within a Kafka (Redpanda) broker. These pipelines are adept at managing low-latency, high-data-volume scenarios.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
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The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
A SYSTEMATIC RISK ASSESSMENT APPROACH FOR SECURING THE SMART IRRIGATION SYSTEMSIJNSA Journal
The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
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ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
1. MODUL KE 6
PERTEMUAN KE 9
RENI KARNO KINASIH, S.T.,M.T.
UNIVERSITAS MERCU BUANA
Model Matematik Lalu
Lintas
2. Penggunaan sistem kontrol traffic light pada lalu lintas
belum memberikan prioritas berupa nyala lampu hijau
lebih lama pada jalur-jalur yang lebih padat
penggunanya.
Hal tersebut dapat menyebabkan antrian panjang pada
sebuah ruas.
Sehingga bila dilihat secara gambaran besar, sistem
kontrol traffic light yang ada ternyata belum maksimal.
Belum adanya informasi yang bisa kita andalkan untuk
memberikan prioritas atau mengambil keputusan.
Bahkan sering kali justru sistem kontrol traffic light lah
yang membuat kemacetan pada sebuah ruas.
3. Dalam simulasi traffic light, untuk menganalisa arus
kendaraan pada sebuah ruas, terdapat beberapa
metode yang bisa diterapkan. Diantaranya metode
Greenshield, teori antrian dan metode
Computational Fluid Dynamic
4. Model Greenshield
Berguna untuk membantu peneliti dibidang
transportasi dalam memahami arus tanpa
hambatan.
Model ini memberikan rumusan matematika arus
kendaraan sebagai fungsi dari kepadatan lalu-lintas,
serta arus kendaraan sebagai fungsi dari kecepatan
kendaraan.
Akan tetapi, model greenshields tidak dapat
mengatasi kerumitan yang dihasilkan oleh kondisi
arus yang memiliki hambatan.
5. Interrupted Flow
Arus dikatakan memiliki hambatan, jika arus lalu-
lintas terhenti secara periodik yang disebabkan oleh
rambu-rambu lalulintas.
Arus yang berhambatan itu memerlukan
pemahaman teori antrian, yang sepenuhnya
merupakan model terpisah dari model arus lalu
lintas
6. Teori Antrian
Teori antrian dapat digunakan untuk menganalisis arus
lalu-lintas melalui pendekatan sebuah persimpangan
jalan yang dikontrol oleh rambu lalu-lintas.
Namun teori ini harus memiliki asumsi bahwa arus
kendaraan harus dalam keadaan rapi dan tidak fleksibel.
Sehingga diperlukan metode yang dapat digunakan
untuk mengatasi permasalahan ini . Salah satunya
adalah metode Computational Fluid Dynamic.
Computational Fluid Dynamic (CFD) adalah metode
yang digunakan untuk menganalisis aliran fluida atau air
7. Computational Fluid Dynamic (CFD)
Adalah metode yang digunakan untuk menganalisis
aliran fluida atau air, namun seiring perkembangan
zaman, metode ini mulai diterapkan di bidang
engineering, salah satunya adalah transportasi
CFD juga dapat memainkan peran penting dalam
mengatur waktu sinyal, sesuai dengan kondisi lalu
lintas, sehingga akan menjamin arus lalu lintas
seragam bahkan ketika tingkat aliran tinggi
8. How CFD Works?
CFD menganalisa aliran fluida dengan cara pemodelan
matematika (persamaan diferensial parsial), metode
numerik (diskritisasi dan solusi teknik) dan perangkat
lunak (pemecah, pra-dan utilitas postprocessing)
CFD menggunakan sudut pandang Eulerian, yakni bukan
memandang kendaraan secara individual dalam aliran,
tetapi memandang arus lalu lintas sebagai aliran
sederhana yang didistribusikan secara terus menerus,
dengan melihat kesenjangan atau selang yang konsisten
antara jumlah mobil dengan panjang jalan yang dikenal
sebagai density.
Penekanan metode CFD adalah pada aliran secara
keseluruhan atau sistem dan bukan pada individu
kendaraan.
9. CFD memungkinkan untuk melakukan eksperimen
berupa perhitungan numerik dan simulasi komputer.
Sedangkan metode yang digunakan untuk menghitung
waktu nyala lampu lalu lintas adalahaturan Manual
Kapasitas Jalan Indonesia (MKJI)
Computational Fluid Dynamic merupakan metode yang
digunakanuntuk dapat menganalisis keadaan arus
antrian pada ruas jalan. Sedangkan aturan MKJI
digunakan untuk mendapatkan nilai kapasitas jalan,
waktu nyala lampu lalu lintas dan derajat kejenuhan
11. Greenshiled’s Linear Model (1935)
Macroscopic stream models represent how the
behaviour of one parameter of traffic flow changes
with respect to another.
Most important among them is the relation between
speed and density. The first and most simple relation
between them is proposed by Greenshield.
Greenshield assumed a linear speed-density
relationship as illustrated in figure 1 to derive the
model.
12.
13. The equation for this relationship is shown below.
………………………. (1)
Where v is the mean speed at density , vf is the free
speed and kj is the jam density. T
This equation (1) is often referred to as the Greenshields'
model. It indicates that when density becomes zero,
speed approaches free flow speed (ie. V vf when k
0).
14.
15. Once the relation between speed and flow is
established, the relation with flow can be derived.
This relation between flow and density is parabolic
in shape and is shown in figure 3. Also, we know that
16.
17. Now substituting equation 1 in equation 2, we get
………………….. (3)
Similarly we can find the relation between speed and
flow. For this, put in equation 1 and solving, we get
………………….. (4)
18. This relationship is again parabolic and is shown in
figure 2.
Once the relationship between the fundamental
variables of traffic flow is established, the boundary
conditions can be derived.
The boundary conditions that are of interest are jam
density, freeflow speed, and maximum flow.
To find density at maximum flow, differentiate
equation 3 with respect to and equate it to zero. ie.,
19.
20. Denoting the density corresponding to maximum flow as k0,
Therefore, density corresponding to maximum flow is half the
jam density Once we get , we can derive for maximum
flow, qmax. Substituting equation 5 in equation 3
21. Thus the maximum flow is one fourth the product of
free flow and jam density. Finally to get the speed at
maximum flow, v0, substitute equation 5 in equation 1
and solving we get,
……………………………………… (6)
Therefore, speed at maximum flow is half of the free
speed.
22. Calibration of Greenshield's model
Inorder to use this model for any traffic stream, one
should get the boundary values, especially free flow
speed (vf) and jam density (kj).
This has to be obtained by field survey and this is
called calibration process.
Although it is difficult to determine exact free flow
speed and jam density directly from the field,
approximate values can be obtained from a number
of speed and density observations and then fitting a
linear equation between them.
23. Let the linear equation be y = ax = b such that y is
density, k and x denotes the speed v. Using linear
regression method, coefficients a and b can be
solved as,
(7)
(8)
24. Alternate method of solving for b is,
……(9)
where xi and yi are the samples, n is the number of
samples, and are the mean of xi
and yi respectively.
25. Problem
For the following data on speed and density,
determine the parameters of the Greenshields'
model. Also find the maximum flow and density
corresponding to a speed of 30 km/hr.
26. Solution
Denoting y = v and x = k, solve for a and b using
equation 8 and equation 9. The solution is tabulated
as shown below.
Step 1
27. Step 2: From equation 9, define b = ….. And a =……
Step 3: Define the linear regression from Step 2
above
v =……. (10)
Here vf = …….. and vf/kj= …….. This implies, =
……/…….. = …….. veh/km
The basic parameters of Greenshield's model are free
flow speed and jam density and they are obtained as
….. kmph and ……… veh/km respectively.
28. To find maximum flow, use equation 6
q max = …… veh/hr
Density corresponding to the speed 30 km/hr can be
found out by substituting in equation 10. i.e,
30 = 40.8 - 0.2 k
Therefore, k = ………. veh/km
29. G R E E N B E R G ’ S A N D U N D E R W O O D ’ S
Other macroscopic
stream models
30. In Greenshield's model, linear relationship
between speed and density was assumed. But in
field we can hardly find such a relationship
between speed and density.
Therefore, the validity of Greenshields' model was
questioned and many other models came up.
Prominent among them are Greenberg's
logarithmic model, Underwood's exponential
model, Pipe's generalized model, and multiregime
models. These are briefly discussed below.
32. This model has gained very good popularity because
this model can be derived analytically. (This
derivation is beyond the scope of this notes).
However, main drawbacks of this model is that as
density tends to zero, speed tends to infinity. This
shows the inability of the model to predict the speeds
at lower densities.
33. Underwood's exponential model
Trying to overcome the limitation of Greenberg's
model, Underwood put forward an exponential
model as shown below.
…………………………………… (12)
Where vf The model can be graphically expressed as
in figure 5 is the free flow speed and k0 is the
optimum density, i.e. the densty corresponding to
the maximum flow.
34. In this model, speed becomes zero only when density
reaches infinity which is the drawback of this model.
Hence this cannot be used for predicting speeds at
high densities.
35. Pipes' generalized model
Further developments were made with the
introduction of a new parameter (n) to provide for a
more generalised modelling approach. Pipes
proposed a model shown by the following equation.
……………………………………(13)
When is set to one, Pipe's model resembles
Greenshields' model. Thus by varying the values of ,
a family of models can be developed.
36. Multiregime models
All the above models are based on the assumption that
the same speed-density relation is valid for the entire
range of densities seen in traffic streams.
Therefore, these models are called single-regime models.
However, human behaviour will be different at different
densities. This is corraborated with field observations
which shows different relations at different range of
densities.
Therefore, the speed-density relation will also be
different in different zones of densities.
Based on this concept, many models were proposed
generally called multi-regime models. The most simple
one is called a two-regime model, where separate
equations are used to represent the speed-density
relation at congested and uncongested traffic.