Hot Jets and Sources of Jet Noise

Abstract

A prediction method based on the generalized acoustic analogy is presented and used to evaluate aerodynamic noise radiated from high-speed hot jets. The set of Euler equations are divided into two sets of equations that govern what may be considered as a non-radiating base flow plus its residual components. Under certain conditions, the residual equations are rearranged to form a wave equation. This equation consists of a third-order wave operator, plus a number of non-linear terms that are regarded as the equivalent sources of sound and their statistical characteristics are modeled. A specialized RANS solver provides the base flow as well as the variance in both velocity and thermal fluctuations that determine the source strength. The main objective here is to evaluate the relative contribution from various source components to the far-field spectra and to show the significance of temperature fluctuations as a potential source of aerodynamic noise in hot jets.