like i said earlier in this topic

if you want to see air flow use smoke and a fan.
just use a smoke bomb infront of a nice big fan(shop fan,box fan) and you will see where the air flows fastest,creates pockets, causes drag,etc.

i dont remember from high school about wind speed and mph if they are equal (1mph speed=1 mph wind) but im sure someone here can remind us.
hell if i was still at work i can borrow an actual air flow measuring device from one of the tin knockers (they use it to test a/c air flow)and test out my leaf blower and convert it to mph. then set my truck down and see exactly where the air flow is best.