Variation of Drag Coefficient, Wall Static Pressure and Secondary Flow Over Passenger Car

Abstract

The present experimental investigation includes finding the variation of drag coefficient, wall static pressures, and aerodynamic drag over a vehicle for twenty-six different orientations of vehicle. The flow was controlled using the submerged type vortex generator (VG) in combination with the rear spoiler during the investigation. The model of a vehicle was fabricated on the reducing scale (15:1) using the Plaster of Paris (PoP). Primarily, the vehicle was tested at the different incidence yaw angles to obtain the total
drag over the model. Further, twenty-six different combinations obtained by changing the flow angles (β = 0 and ±30°), spoiler angles (α =0 and ±45°) and orientations of VGs were tested. A variation of static pressures and drag coefficients for all combinations was analyzed. Further, the development of secondary-flow was also traced. Secondary flow becomes important as it causes a sheared flow produced near the body and wall of a sadden vehicle which further deflects the air pressure on the roof of the vehicle body. The variation of the secondary flow was obtained with the wall static pressure, surface static pressure and boundary layer by changing the flow angles ( β = 0 and ±30°), and spoiler angles (α =0 and ±45°) and orientations of VGs. The best combination in terms of surface static pressure coefficient (Cwp) rise (from –0.041 to +2.622) is found at β = 0°, α = 0° and the VG attached to the upstream of the spoiler. CFD analysis is conducted using ANSYS FLUENT® and Solid Works was used for building the geometries of the car and
spoiler. A formulated computational fluid dynamics model is in good match with the experimental results.