Here's the picture of the result. You can see that the strongest conclusion is that there's turbulence, but I can get an idea of the direction of airflow by taking the approximate average of where the paint is, and it is out towards the side of the car a bit. In fact it looks almost in line with the angle of the side edge of the airdam.
Since my departure's delayed, I might mess around with coming up with some wheel deflectors tomorrow.