Quote:
Originally Posted by twinair
My statement isn't about streamlining, it's about the effect of the distance between road surface and bottom of a parallel surface on pure shear forces (and that these shear forces wouldn't be substantial, since it is not practical to lower the car to a point, where these shear forces would start to play a significant role).
Maybe there are other detrimental effects than increased shear forces which may start to play a role when lowering a car.
Can you show any data that shows that lowering a passenger car has increased aerodynamic resistance?
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I came up with 3-pages of notes with respect to lowering.
*The first thing which concerns your formula is that the boundary layer is turbulent and typically the flow is turbulent.Shearing forces aren't really present because of the thickening boundary layer.
The turbulence itself is the issue,as the rotational kinetic energy cannot be converted to useful pressure.
*Ground clearance effects will be affected by:
# degree of underbody roughness (R.G.S.White of MIRA allowed a rating of 1-5 as a degree of roughness)
# body inclination
# body camber
# presence of an airdam
# presence of a diffuser
# variability of wheel/tire/wheel covers
# presence of wheel fairings
# wheelhouse volume
# cooling system extractors
# rocker panel depth
There are just too many variables within the product mix to make 'one-size-fits-all' high confidence predictions.
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Historically,the lowest drag concept cars have full underbody paneling as well as active suspension to lower the car at highway speed.
The Cd 0.152 Ford Probe-IV extends its active airdam, lowers its nose to 3.1-inches G.C., then hikes its booty to achieve the ideal body inclination for lowest drag.
The C.G. is benefited as an aside.
I suspect that the 1985 Cd 0.137 Ford Probe-V is doing likewise although no published data exist so far on that one.