Instead of modeling, how about measuring? Mount this little sucker just behind the front mesh or just under the car at various locations and see what the airspeed velocity really is. If you really wanted to you could run a section of brake duct and cut it off before it gets to the brake and afix this to a piece of hardpipe attached at the end of the brake duct and measure the velocity where you most care about. It goes up to 56 m/s (or about 125 mph), hooks up to your i-phone, it is cheap, and gives you real data without the modeling error. Doesn't accomplish the modeling of the whole car but would more than suffice for detecting high pressure areas where you could put cooling ducts.
come on calvin you are engineer that would be to logical