On jet aircraft, portions of the engine nozzle usually swivel around the end of the nozzle blocking the exhaust coming out of the engine. Though they are not necessary for landing, the reason thrust reversers are so common is that they significantly reduce the distance needed to land an aircraft. Not only does this mean aircraft can land on shorter runways and at smaller airports, but it also greatly reduces the time needed to stop the aircraft before it can begin its taxi to the gate. If you've ever opened up the stopper in a sink full of water and watched the water swirl down the drain, you know what a vortex is. Simply put, it is an energetic swirling mass of fluid.
Vortices are quite common in aerodynamics.
Probably the most well-known and significant of these are the trailing vortices that are seen coming off the tips of wings in flight. However, vortices very similar to trailing vortices can also be used to produce beneficial effects, and one of the methods used to create beneficial vortices is the vortex generator. In previous questions, we have discussed the concept of flow separation. 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 .