Quote:
Originally Posted by backpacker3
Hey guys sorry if this gets posted a lot I had just seen some things that said that adding dimples works and just thought I would post this.
Xist the I saw the mythbusters episode too that's where the idea came from I didn't realize the general consensus here was that it didn't work. I figured that it might be useful for someone who maybe had removed roof rails or something
Ike that as an option to cover the roof of the car with something that might help a little bit for fuel economy. But hey if this end up corralled or closed it was just a though so no big deal
Not that it really matters at this point but if you put some masking or painters tape on the outside of the balls they would come out easy.
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I want to say that it was Slowmover who shared a link to an Ethiopian gentleman's Masters Thesis on pickup truck aerodynamics.I've looked back and can't find the post.Sorry!
Anyway,within the thesis,the author reported that the pickup maintained 30 millimeters of Laminar Boundary Layer (LBL) at the nose before transition to full Turbulent Boundary Layer (TBL).Which means that without any 'dimpling',the truck was behaving as fully-dimpled within just over 1-inch distance from its nose.
The TBL would create a constant drag coefficient and the separation line would be fixed.
If any benefit came to the Mythbusters' car it would not have been from the Reynolds number effect,but rather from the dimpling along the roof /C-pillars acting as vortex generators.
The second drive of the car would also have been conducted under a 'warmer' condition which always improves mpg.
Only full instrumentation of the car would have revealed a full and accurate account of all the variables at play during 'testing.'