[DeTomaso] SORC # 135 Pictures

[Daniel C Jones]

> I think those devises redirect or concentrate air flow, not keep it from
separating from the surface.

Vortex generators reduce drag (or delay stall) by tripping the boundary
layer from laminar to turbulent flow which delays separation.  That
generally increases the skin friction but decreases the pressure drag which
is usually the larger component.  If you can maintain laminar flow without
separation, that has lower drag.  In the case of hood, I'd be surprised if
there is separation and don't think VGs would be of much use.  An easy test
is to tape yarn strings to the hood.  If they streamline, the flow is
laminar.  If they moved around a bunch, it's turbulent.  If they are still,
there's separation.

Dan Jones
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   > I think those devises redirect or concentrate air flow, not keep it
   from separating from the surface.A
   Vortex generators reduce drag (or delay stall) by tripping the boundary
   layer from laminar to turbulent flow which delays separation.A  That
   generally increases the skin friction but decreases the pressure drag
   which is usually the larger component.A  If you can maintain laminar
   flow without separation, that has lower drag.A  In the case of hood,
   I'd be surprised if there is separation and don't think VGs would be of
   much use.A  An easy test is to tape yarn strings to the hood.A  If they
   streamline, the flow is laminar.A  If they moved around a bunch, it's
   turbulent.A  If they are still, there's separation.
   Dan Jones