Quote:
Originally Posted by JulianEdgar
Yes, very interesting - and thanks for reminding me.
But if we look at the angle of that rear bumper taper, and do a forward force triangle diagram from that increase in pressure, it has to be really tiny ie the taper wouldn't be more than about 10 degrees, would it?
But I can certainly see a change in pressure there having an influence on the wake pattern.
I posted my video to Linkedin, and I have some contacts there who are professional aero people - both CFD and wind tunnel. I've asked if they have any ideas about the relationship between side pressures / degree of attachment and resulting drag.
I just always took it on face value that 'improved side flow attachment = lower drag' but like all aspects of car aero, the more you think about it, the less you realise you know.
|
1) If flow attachment can be maintained for the entire length of the body, on a body of progressive cross-sectional contraction, by default, the pressure existing at the separation line will be the highest achievable, translating to highest base pressure ( for that length ), lower pressure drag, and lower overall drag.
2) Minimizing separation is the drag reduction.
3) Un-rounding the curvature, but maintaining a streamlined profile, provided a little extra pressure recovery on the sides, with a drag reduction reward.