Optimization on Wind Tunnel and Spoiler by using CAE Tools

In high speed cars of sedan class, there comes a major problem of lack of grip on road while running at high speeds. This problem comes due to the geometry of the car’s outer body. This can be understood by considering the fact that while running, the upper and lower surface relative wind streams have to meet themselves on the back side of the car at the same time. Now the shape of the sedan class cars outer body is such that, while running, the relative wind has to travel a larger distance at the upper surface rather than the lower surface. Now, to fulfill this requirement the upper surface relative wind velocity has to be greater than that of the lower surface relative wind. Hence pressure on the upper side of the car drops with respect to the lower surface at high speeds. This pressure difference between upper and lower surfaces of the car creates an upwards lift force which adversely affects the road grip of the car at high speed. The same phenomenon works on the airplane wings to give it the required lift force. This is because of the resemblance between the outer body- geometry of sedan cars and the airplane wing’s profile. The profile or cross section of airplane wings is called airfoil. So due to airfoil like shape of sedans they experience an unwanted lift force at high speeds. Now, to overcome this problem a wing type structure is incorporated on the rear side of the car which is called back air spoiler or simply a spoiler. A spoiler was fabricated and tested at different wind velocities on Wind Tunnel in Faridabad and the tests yielded the respective lift and drag coefficients. It was noticed that as the wind velocity was decreasing lift and drag coefficients were increasing. At the same time the lift to drag ratio was also increasing. Thereafter the two dimensional CFD analysis of fabricated spoiler’s cross section was carried out on ANSYS 14.0. Fluent workbench on a single velocity and the respective flow variables such as pressure contours, velocity contours, path line etc. were presented. Thereafter the three d dimensional simulation of flow over the fabricated spoiler was carried out on the ANSYS 14.0. workbench.