The primary noise sources associated with turbulent Coanda wall jets

Abstract

A wide variety of aeronautical and aerospace applications utilize the Coanda effect. However, due to the enhanced turbulence levels observed with devices using this effect, turbulent mixing noise is a primary noise source. For supersonic jets close to Coanda surfaces, shock‐associated noise (both broadband and screech tones) is also a significant source of sound. A theory has been developed to predict the turbulent mixing noise emitted by unit‐volume of jet‐type shear‐layer turbulence close to a rigid plane, and extended to a plane two‐dimensional wall‐jet. However, most flows of practical interest are three‐dimensional and, in the case of the Coanda jets, exhibit significant curvature. This paper extends the previous models for turbulent mixing noise to predict the aeroacoustic characteristics of a three‐dimensional turbulent flow over a Coanda surface. Details of experimental observations of the shock‐cell structure associated with supersonic Coanda wall jets, and a method of modeling the corresponding shock‐associated noise, is also discussed.