Quote:
Originally Posted by freebeard
Vas ist das?
I don't pretend to understand, but I'm hopeful. But then I'm still hopeful about the Scuderi Cycle engine.
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1) where the attached flow separates from the body is, by definition, the separation line. The back of a truck box, or trailer van in this case.
2) turbulent boundary layer flow will easily remain laminar if it's flowing towards a low pressure ( just ahead of the windshield header/ roof apex ).
3) beyond this location of lowest pressure, the turbulent boundary layer is in jeopardy of separation if it encounters pressure which is increasing any faster than it would over a 'streamlined' body ( template).
4) the pressure is governed by how rapidly the body cross-section reduces, which causes a pressure rise as it gives up its position of displacement, attempting to get back where it was before we came along. Loitering in place.( Bernoulli Theorem ).
5) all a streamline body does is, give the air twice as much distance to slow back down, as was used to accelerate it from rest. You can actually measure this with string. It's a fast pelagic fish profile ( bluefin tuna viewed from the top ) with 1/3rd of the body accelerating the air from rest, and the remaining 2/3rds as a deceleration ramp, long enough to let the air recover its former, pre-vehicle position. It's the perfect ratio of accel/ decel. Anything more aggressive and the pressure rise exceeds what the boundary layer can tolerate.
6) all the air in the back of the car wants to go to the windshield. Outer flow, above the boundary layer strafes the boundary layer, shooting kinetic energy at it by way of glancing blows. If the surface of the car falls away to rapidly, the bullets of air just ricochet off the top of the boundary layer like a flat stone on a pond, making it impossible to hold the layer in place.
7) once this angle grows beyond streamlined, the layer begins to flow forwards to the windshield, rolling up into eddies, then lifting off the car ( separation ), in full-blown turbulence.
8) turbulence is pure entropy. It's an irreversible loss of kinetic energy. It can never be recovered by any means, and literally heats the air around it until warn down by viscous forces, hundreds of feet behind the car. The plasma-actuators do nothing to address this issue.
9) without streamlining, all we have is a wake of turbulence. Useless! Costly. Low performance.