In 'real' flow, any alteration to an automobile body would affect downstream as well as upstream flow. It wouldn't be isolated to any specific region of the body.
I've taken high static pressure, high velocity blowers to a car, and while the results are 'way out ahead of nothin',' I never had any expectation that what I observed could be repeated in a laboratory.
As to 'laminar' and 'turbulent' flow............. if the tufts aren't going crazy, jumping all over the body panel, you might as well presume that you've got laminar flow based on a turbulent boundary layer from the blower blast. It only takes a 20-mph 'wind' to achieve a turbulent boundary layer ( whole car ).
If a neighbor or friends can drive a chase car, and videograph of photograph tufts, that's better, as long as they're not so close as to alter the airflow them selves.
MetroMPG has, for years, solved the 'lack of chase car' syndrome, by attaching a GoPro or similar device to a stand-off strut on the test car itself, allowing autonomous capture of the tuft flow by himself. Clever!
