Check out the new Speed Demon wind tunnel test with lots of cool photos and a smoke trail video at: http://hotrodenginetech.com/smokin-the-speed-demon/
One of the better aspects of this sort of car is that with the wheels being almost completely shrouded the fact that the tunnel does not have a moving ground plane has a little less effect on skewing the results. As noted in the article the fact that the testing is done at low air speeds also makes the results more of a guideline than absolute fact. A friend on mine built scale models for NASCAR team testing and they actually drew air in through the intake plenum and pushed it out the headers while the car ran on a moving ground plane tunnel with the wheels turning. The models cost more than a full size rolling chassis. When we ran funny cars in GM's tunnel we could not simulate the growth of the rear ties and the turbulence that they created under the back of the car and we also did not have two huge columns of hot exhaust gas from the headers affecting the air flow down the sides of the body. We did use smoke to see from how far out on the hood surface the air was drawn into the opening around the injector hat but for the flow on the rear deck and spoiler I usually wool tufted. I don't know how high the airspeed in the Darko tunnel in the video is and maybe that ran it faster without the guy in place with the smoke wand but we tested at 130 mph and the software extrapolated the numbers to come up with 300 mph downforce and drag references. Roo
Does the air flow change significantly at higher speed? The air looked to be 30-50? mph in the video, since the guy could stand up and move around. Will the lower speed air yield results that will be consistent at 300-400 mph?
Probably not so much with a slick shape like a streamliner but with bodies that have more pronounced transitions between surfaces the speed of the airflow over the body can make a difference. The higher end software used to extrapolate the results should have the capability of factoring that into the results. Roo
Spent a week at George's place back in '12 and had some very interesting conversations with him every afternoon... He will be the first over 500 in a piston engined car. 1st gen SBC nonetheless!
sure is good to see the demon come back! now if we can get the salt back. the best of luck to you George.