Flow interaction between two Cars in windtunnel and in Environment

1. Flow interaction between two Cars in windtunnel and in Environment By: Ahmad Gohari FarhadJebelisinaki

2. 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

3. 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

4. Geometry and meshLength of windtunnel: 50 metersHeight of windtinnel: 10 meterwe consider enough space in front and in the back of the cars

5. Mesh Quality test95.6% of mesh are equi-size94.2% equi-angle

6. 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)

7. Fluentadapt boundary mesh by Fluent

8. Results for speed of 70 km/hModel of simulation: first orderContour of velocity and Pressure Pressure contour Velocity contoue

9. Model of simulation: first orderforce report 140 km/h 70 km/h

10. Fleuntmodeling order: second order 140 km/h 70 km/h

11. Force reportsecond order 140 km/h 70 km/h

12. Now we investigate the cars in a windtunnel with height of 3.5 meters and compare the resultsdistance between cars 3 metersspeed 70 km/h Force report

13. Now we investigate the cars in a windtunnel with height of 3.5 meters and compare the resultsdistance between cars 3 metersspeed: 140 km/h

14. 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

15. Distance between cars: 3 metersCars are moving in environment Force report

16. 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

17. When force interaction between cars become negligible? (70 km/h)

18. When force inteaction between cars become negligible? (140 km/h)

19. In the distance of 40 we can consider the force difference can be negligible, indeed there’s no interaction between carsspeed: 70 km/h

20. In the distance of 40 we can consider the force difference can be negligible, indeed there’s no interaction between carsspeed: 140 km/h

21. 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.