Quote:
Originally Posted by lunarhighway
an interesting idea... i've always wondered it it was possible to design a sort of "wing"in the broad sense of the word, that in stead of generating lift at the top would generate pressure at the end... there would naturally be a loss of energy, but if this shape could be roughly car like than you'd have a car that in stead of having drag at the end would have pressure at the end.
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You are right, this does act much like a wing does*. A 'normal' airfoil uses convex curves to accelerate local flow to create lower-than-ambient pressure, which we call lift. In much the same way this setup uses concave curves to decelerate local flow to create higher-than-ambient pressure which is put to work as thrust.
With this thrust force in place, the aero design goal goes from low drag to maximum efficiency. The tests done so far point to max efficiency coming when the pressure thrust force counteracts ~90% of the aero drag & the remaining propulsion comes from the traditional drivetrain.
If only the ALMS Green Challenge races allowed the use of 'movable aerodynamic devices,' those race teams would make short work of working out the details and optimizing the different tradeoffs.
-Dave B
*I've simplified this to take it easy on my poor brain... I'm not trying to open the whole 'why-do-airfoils-make-lift' case of worms.