How do vortex generators work on aircraft wings or BMW roofs?

When an aircraft flies at high angles of attack, the airflow over the wing can become detached, or it stops following the shape of the wing. When this happens, the lift produced by the wing will suddenly and rapidly decrease, and the wing is said to be stalled. When the flow separates from the wing, it usually means the air is moving too slowly, or there isn't enough energy in the flow to keep it moving. Since vortices are energetic, they can be used to put energy back into the flow to keep it moving in the desired direction. This is what vortex generators are designed to do.



Vortex generators are simply small rectangular plates that stick out above the wing surface. They look like tiny little wings jutting up perpendicular to the wing itself. As air moves past them, vortices are created off the tips of the generators just like the trailing vortices mentioned earlier. These vortices interact with the rest of the air moving over the wing to speed it up and help reduce the possibility of separation.



I think on the BMW it is just an antenna. We have no probs with BMW roofs stalling. :)How do vortex generators work on aircraft wings or BMW roofs?Vortex generators mix the air on the upper surface of the wing, therefore preventing airflow separation at various speeds and aircraft attitudes. They actually produce a little bit of drag to prevent greater turbulence. Greater turbulence would inhibit airflow to reach the control surfaces, therefore diminishing aircraft control.



On the roof of a BMW, I can only assume they "mix" the air so the air reaches the rear spoiler more effectively, hence creating down force on the rear spoiler. However, you would have to go very fast for those vortex generators to make any real difference.