On the Role of Flow-Acoustic Interaction in Noise Directivity of a Subsonic Isothermal Jet

In this paper, the far-field noise emanating from a single subsonic isothermal jet at several angles with respect to the jet axis is considered. Since our aim is to study noise directivity, convection and refraction effects must certainly be taken into account. Hence, a high frequency solution to the axisymmetric Lilley’s equation, which is a re-arrangement of continuity and momentum equations, is employed to figure out the SPL in the frequency range of interest at several angles with respect to the jet axis. Also, to describe sound generation sources in the flow, the standard k-ε model is used whose output provides the required input for solving noise problem. Finally, considering a suitable acoustic time-scale, best possible results in comparison with experimental data are presented. Results disclose a good agreement between noise predictions and observations. It is demonstrated that the accuracy of the prediction is good, being typically a few dB at worst.

Keywords:

Aerodynamic noise , Subsonic jet , Aeroacoustics , Flow-acoustic interaction