Quote:
Originally Posted by aerohead
With zero-yaw flow,for a leading edge,your after just enough radius to get the flow attached,which would be a fraction of the body width,or a fraction of the square-root of the frontal area.It's been researched both ways.
If you do the blown slot as shown,the upper surface is above the plane of the roof,which is separation right there.
The slot introduces a jet of air which disrupts the pressure profile of the air around it,adding an aerodynamic 'kink',to the body,and it aggravates the growth of the local boundary layer,which we'd like to minimize as much as possible,as well as have as uniform as possible.
For crosswind conditions (mostly the real world of motoring) a bulbous nose has an advantage over all other leading edges.
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The radiused add-on's upper surface would be a fraction of an inch above the plane of the surface; I agree it is a disturbance, albeit a small and smooth one, with induced surface flow...
It is in the yawed flow, where the free stream flow is flowing away from the plane of the surface, where the slot might contribute to delay separation? The stronger the yaw, the stronger the slot should perform, and perform similar to a slotted wing to improve attachment? It sure benefits wings at high yaws! It's also known that wing slots are hurtful at low yaws, so maybe the net-net benefit for slots is negative, unless the plane of the surface normally falls away from the free-stream flow?