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Turbulent Coanda wall jets are present in a multitude of natural and man-made applications. Their obvious advantages in terms of flow deflection are often outweighed by disadvantages related to the increased noise levels associated with these jets. Primary high-frequency noise sources are turbulent mixing noise (TMN) and shock-associated noise (SAN). Clearly, accurate modeling of these noise sources will facilitate better predictions of the behavior of such jet noise with physical characteristics. This paper, which focuses on SAN, shows how the Method of Characteristics can be applied to a steady two-dimensional axisymmetric supersonic flow to rewrite the three governing partial differential equations in terms of two ordinary differential equations; the characteristic equation and the compatibility equation. The Euler predictor-corrector numerical integration algorithm is then used to rewrite these equations as finite difference equations and solve them at points in the flare jet flow field immediately downstream of the nozzle exit. In this way, the shock cell structure associated with a particular turbulent Coanda jet is estimated, and these predictions are compared with experimental results obtained using flow visualisation techniques. Ultimately it is hoped that this will allow the Coanda effect to be more widely applied, and its potential to be fully realized.
Lubert, C. P., Schwantes, C. R., & Shafer, R. J. (2016). An Investigation of Initial Shock Cell Formation in Turbulent CoandaWall Jets. International Journal Of Acoustics & Vibration, 21(2), 199-208. doi:10.20855/ijav.2016.21.2413