In aerospace industry, chevrons are the sawtooth patterns on the trailing edges of some jet engine nozzles that are used for noise reduction. Their principle of operation is that, as hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces noise-creating turbulence. Chevrons were developed with the help of NASA. Some notable examples of such engines include GEnx and Rolls-Royce Trent 1000.