Re: How stalled diffuser/wing decrease drag?
Posted: 22 Dec 2023, 17:59
I calculated for 67m/s and sea level pressure 101325 Pa , I get it -63 168 Pa, this is -0.6bar, this sound impossible to get so high suction at the wing!!
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Re: How stalled diffuser/wing decrease drag?
Posted: 22 Dec 2023, 22:53
I got 0.55 bar static pressure on that point, but yeah, it's possible. It's very local, remember that. Cp of -8 is more spread in that example, which is "only" 0.8b static pressure and that's far more reasonable
Re: How stalled diffuser/wing decrease drag?
Posted: 22 Dec 2023, 23:16
-17=p-101325 /(0.5x1kg/m3x67m/s^2)
p=63168 Pa is static pressure, barometric pressure
I made mistake..... 63168 Pa -101325 Pa = suction is -38 157 Pa this is -0.38bar, still big
67m/s is 241km/h,F1 car speeds
Re: How stalled diffuser/wing decrease drag?
Posted: 23 Dec 2023, 00:55
Am I the only one thinking that by the time (before, actually) your model gets a supersonic region, neither your equations (no longer incompressible fluid) are adequate nor your wind tunnel (different supersonic point) is realistic?
I was under the impression that these models break down well before supersonic anything.
I was under the impression that these models break down well before supersonic anything.
Re: How stalled diffuser/wing decrease drag?
Posted: 23 Dec 2023, 20:27
Good point. I would have to jog my memory to be honest, but yeah the local supersonic flow is changing things. I haven't been studying transonic nor supersonic flows a lot after my studies. The local supersonic flow leads to drag divergence due to local normal shockwave generation, but I can't tell how it infulences local pressure field and if subsonic coefficient calculations are valid. Supersonic flow (global) has very different coefficient expression, but I don't know what happens with local supersonic cases.hollus wrote: ↑23 Dec 2023, 00:55Am I the only one thinking that by the time (before, actually) your model gets a supersonic region, neither your equations (no longer incompressible fluid) are adequate nor your wind tunnel (different supersonic point) is realistic?
I was under the impression that these models break down well before supersonic anything.
Re: How stalled diffuser/wing decrease drag?
Posted: 03 Jan 2024, 08:54
Do you know which NACA profiles they use for rear main wing and flap?Vanja #66 wrote: ↑23 Dec 2023, 20:27Good point. I would have to jog my memory to be honest, but yeah the local supersonic flow is changing things. I haven't been studying transonic nor supersonic flows a lot after my studies. The local supersonic flow leads to drag divergence due to local normal shockwave generation, but I can't tell how it infulences local pressure field and if subsonic coefficient calculations are valid. Supersonic flow (global) has very different coefficient expression, but I don't know what happens with local supersonic cases.hollus wrote: ↑23 Dec 2023, 00:55Am I the only one thinking that by the time (before, actually) your model gets a supersonic region, neither your equations (no longer incompressible fluid) are adequate nor your wind tunnel (different supersonic point) is realistic?
I was under the impression that these models break down well before supersonic anything.
Re: How stalled diffuser/wing decrease drag?
Posted: 03 Jan 2024, 11:30
Re: How stalled diffuser/wing decrease drag?
Posted: 03 Jan 2024, 13:31
Re: How stalled diffuser/wing decrease drag?
Posted: 03 Jan 2024, 15:11
F1 wing profiles are not from any aerofoil family. They're drawn parametrically by eye and experience using splines/curves.