Numerical study of the effects of wind-tunnel conditions on a passenger vehicle in crosswinds

Sammanfattning: Wind tunnel tests is a necessity when it comes to study of aerodynamic flow field around vehicle in its development process. However, there are certain limitations on physical wind tunnel tests during vehicle development process. This includes high running costs and interference effects due to blockage and boundary conditions. Hence, one of the main objective of this thesis is to study the effect of these boundary conditions and interference by a physical wind tunnel numerically in a virtual wind tunnel in straightline and steady crosswinds scenario. Furthermore, accuracy of different wind tunnel correction methods is studies. Lastly, effects of rounding of A and C pillars on aerodynamic flow field is investigated. The open scenario is used as a baseline for comparison. Blockage ratio of virtual wind tunnel is 8%. Windsor model with two different backlight angles have been used for this study. It has been observed that solid and wake blockage contribute to an increase in drag in wind tunnel. Furthermore, lift coefficient increases and drag coefficient increases when floow is stationary when compared to moving floor. It is also noted that different correction methods are suitable based on flow characteristics and scenarios considered. It is difficult to understand which method to apply without extensively understanding the flow characteristics. Lastly, rounding of A-pillar results in reduction of drag and lift coefficient for both models. Under yawed condition, rounding of A-pillar results in reduction of yaw moment coefficient. Rounding of C-pillar results in increase in drag coefficient and increase in lift coefficient for Windsor model with 25°slant angle. However, when the same model is kept at yaw, rounding of C-pillar result in reduction in drag coefficient, decrease in lift coefficient and yaw moment coefficient.