Transcript Flow interaction between two Cars

Flow interaction between two Cars
in windtunnel and in Environment
By: Ahmad Gohari
Farhad Jebelisinaki
1
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
2
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
3
Geometry and mesh
Length of windtunnel: 50 meters
Height of windtinnel: 10 meter
we consider enough space in front and in the back of the cars
4
Mesh Quality test
95.6% of mesh are equi-size
94.2% equi-angle
5
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)
6
Fluent
adapt boundary mesh by Fluent
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Results for speed of 70 km/h
Model of simulation: first order
Contour of velocity and Pressure
Velocity contoue
Pressure contour
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Model of simulation: first order
force report
140 km/h
70 km/h
200
180
160
140
120
100
80
60
40
20
0
Car 1
Car 2
Press
Force
Viscous
Force
Total
Force
1400
1200
1000
800
600
400
200
0
Press
Force
Viscous
Force
Total
Force
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Fleunt
modeling order: second order
70 km/h
140 km/h
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Force report
second order
140 km/h
70 km/h
250
200
150
Car 1
Car 2
100
50
0
Pressure Viscous
Force
Force
Total
900
800
700
600
500
400
300
200
100
0
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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 meters
speed 70 km/h
350
300
250
200
Car 1
150
Car 2
100
50
0
Press force Visco force total force
Force report
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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 meters
speed: 140 km/h
1600
1400
1200
1000
800
Car 1
600
Car 2
400
200
0
Press
force
Viscos
force
Total
force
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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 meters
Cars are moving in environment
12000
10000
8000
6000
Car 1
Car 2
4000
2000
0
Press Viscous Total
force Force Force
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)
400
350
300
250
200
Car 1
150
Car 2
100
50
0
10 meters
20 meters
30 meters
40 meters
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When force inteaction between cars
become negligible? (140 km/h)
1600
1400
1200
1000
Car 1
800
Car 2
600
400
200
0
10 meters
20 meters
30 meters
40 meters
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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
400
350
300
250
200
150
100
50
0
Car 1
Car 2
Press
Force
Viscos
force
Total
force
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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
1600
1400
1200
1000
800
Car 1
600
Car 2
400
200
0
Press
force
Viscos
force
Total
force
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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.
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