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Flow interaction between two Cars in windtunnel and in Environment. By: Ahmad Gohari Farhad Jebelisinaki. Introduction. We investigate in this Project: - The air flow modification induced by two cars driving behind each other in a line - PowerPoint PPT Presentation
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Flow interaction between two Cars in windtunnel and in Environment
By: Ahmad GohariFarhad Jebelisinaki
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Introduction
• We investigate in this Project:
- The air flow modification induced by two cars driving behind each other in a line
- It is well-known depending on speed and distance, between two cars there would be a strong interaction
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Consideration
• Distance between two cars is 3 meters• We investigate the cars in a wind tunnel of 70
km/h and 140 km/h of air speed at inlet velocity• We will solve the problem with first and second
order equation and compare them with together• Consideration: Steady state-two dimensional-two
identical cars-turbulent flow-compresible air flow
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Geometry and meshLength of windtunnel: 50 metersHeight of windtinnel: 10 meter
we consider enough space in front and in the back of the cars
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Mesh Quality test95.6% of mesh are equi-size
94.2% equi-angle
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Defining boundary condition in Gambit
• We defined the boundary conditions in Gambit as:
• Velocity inlet• Outflow• Walls• Interior (which is just a line to make the
meshing easy)
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Fluentadapt boundary mesh by Fluent
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Results for speed of 70 km/hModel of simulation: first order
Contour of velocity and Pressure
Velocity contoue Pressure contour
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Model of simulation: first orderforce report
Press Force
Viscous Force
Total Force
0
50
100
150
200
Car 1Car 2
Press Force
Viscous Force
Total Force
0200400600800
100012001400
70 km/h 140 km/h
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Fleuntmodeling order: second order
70 km/h 140 km/h
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Force reportsecond order
Pressure Force
Viscous Force
Total0
50
100
150
200
250
Car 1Car 2
Pres-sure force
Viscous Force
Total Force
0100200300400500600700800900
70 km/h 140 km/h
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Now we investigate the cars in a windtunnel with height of 3.5 meters and compare the results
distance between cars 3 metersspeed 70 km/h
Press force
Visco force
total force0
50
100
150
200
250
300
350
Car 1Car 2
Force report
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Now we investigate the cars in a windtunnel with height of 3.5 meters and compare the resultsdistance between cars 3 meters
speed: 140 km/h
Press force
Viscos force
Total force
0
200
400
600
800
1000
1200
1400
1600
Car 1Car 2
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Consideration in Enviroment
• We had investigated the air-flow for two Cars in a windtunnel. Now we want to simulate the cars in real environment. For this case we would have no velocity inlet (air is at rest in environment) and we would define the velocity of 70 and 140 km/h for two cars. And compare them together.
• In this case there would be boundary condition of 1 bar at inletflow and outflow
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Distance between cars: 3 metersCars are moving in environment
Press force
Viscous Force
Total Force
0
2000
4000
6000
8000
10000
12000
Car 1Car 2
Force report
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When force interaction between cars become negligible? (70 km/h)
• In this case we investigate the force interaction between two cars for 10,20,30,40 meters and compare the force changing in these distances .
• Height of windtunnel: 10 meters
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When force interaction between cars become negligible? (70 km/h)
10 meters 20 meters 30 meters 40 meters0
50
100
150
200
250
300
350
400
Car 1Car 2
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When force inteaction between cars become negligible? (140 km/h)
10 meters 20 meters 30 meters 40 meters0
200
400
600
800
1000
1200
1400
1600
Car 1Car 2
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In the distance of 40 we can consider the force difference can be negligible, indeed there’s no interaction between cars
speed: 70 km/h
Press Force
Viscos force
Total force
050
100150200250300350400
Car 1Car 2
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In the distance of 40 we can consider the force difference can be negligible, indeed there’s no interaction between cars
speed: 140 km/h
Press force
Viscos force
Total force
0
200
400
600
800
1000
1200
1400
1600
Car 1Car 2
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Conclusion• Speed is higher in sharp angels and pressure is lower in sharp
angels and inverse• Viscous force are much less than Pressure forces on the cars• Total pressure on first car is more than the second car• After 40meters body force interaction between cars is
negligible• If speed increases, body force on Cars and air-flow
interaction between cars will increase• A Windtunnel with less height can effect the amount of
velocity,pressure and body forces on Cars, the amount of body forces will increase in a Windtunnel with less height.
