Hit the Road: the Aerodynamics of Cars On-Road
This blog is mainly a summary of what has been done to understand and possibly predict the aerodynamic performance of road cars on road. While it might sound a bit repetitive to say "road cars on road", the fact is a lot of aerodynamic study of road cars are done in a rather calm wind tunnel. That could result in some significant difference from real-world on-road conditions. If only the straight-line drag coefficient is used to predict a car's fuel consumption over a certain cycle, chances are it will be underestimated. To address this, the concept of "wind-averaged drag" is brought forward. First of all, for a given ambient wind condition, the resultant velocity and aerodynamic yaw angle can be calculated using the equations below: V_res = { [V_car + V_wind * cos(theta)]^2 + [V_wind * sin(theta)]^2 )^0.5 Ψ = atan{ [V_wind * sin(theta)] / [V_car + V_wind * cos(theta)] } Wind Speed (V_w), Vehicle Speed (V_v) and Resultant Speed (V_RES) courtesy of ...