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
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