Elimination of screech tone noise in supersonic swirling jets

Imparting a sufficient degree of swirl in underexpanded jets issuing from a convergent nozzle eliminates the quasiperiodic shock cells downstream of the third shock cell, which is also downstream of the flow recirculation zone. Since the existence of the fourth and the fifth shock cells is responsible for the screech tone noise generation, imparting swirl to a supersonic jet can eliminate screech tone noise. Flow recirculation alone does not eliminate the quasiperiodic shock cell structure downstream of the third shock cell. Swirl helps to eliminate the quasiperiodic shock cell structure that is essential for screech tone noise generation.