Quote:
Originally Posted by AeroMcAeroFace
How much do you think (although of course there is no way of knowing without testing) of the benefit of your air curtains come from the increased surface pressures pulling back less, on the tapered sides of the car and how much do you think is thanks to better flow attachment causing better wake patterns?
I suppose my question is, all other things equal, on a non-tapered car would the resultant drag decrease be the same?
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I don't know!
As far as I can find, there is almost no coverage in the tech literature as to the mechanism by which changed side pressures/flow influence drag reduction.
Obviously early separation down the side of the car will enlarge the wake, and via tuft testing, you can see that occurring on some cars (eg from behind the rear wheels). But that doesn't answer the question about cars that have ostensibly attached flow but at lower side pressures.
Aerohead's theory that the pressures of the flow at separation imparts a pressure that's reflected in wake pressure doesn't seem to be supported, although I can see these pressures may
influence wake pressure. It seems to me that wake pressures are much more influenced by vortex behaviour, which just leads us back to the question of how changed side pressures influence vortex behaviour.
Perhaps the higher pressures at side separation give less of an abrupt pressure change to the wake, resulting in weaker vortex formations? (But that seems a bit chicken and the egg.)
I've asked my experts (different thread) about the relationship between trailing panel pressures and wake pressures, but only one has got back to me - not a good time of the year to be asking.
So if you find anything in the tech lit, please let me know!