Has anyone outside of NASA built a truck top wind tunnel?
I can see three options. All involve an automated test sequence while I drone down the local interstate in the small hours.
1. A pole. This may not do a good job of getting out of the disturbed air from the trucks flow field. Going too far forward will give stability problems. Though a rear fin could help.
2. A horizontal splitter plate. If larger than the truck, should give reasonably clean flow? Side cheeks will further help, but I need to keep their ac back to avoid instability.
3. A venturi section. Should be the cleanest, but test section no good for full scale testing and the speed up not enough to get actual Re on scale models.
I can go 8'6" wide and 12'6" high. My s10 sits 5'4" high empty.