Evaluation of subsonic inflow treatments for unsteady jet flow

Linearized Euler simulations of the unsteady flow of a subsonic jet and its associated acoustic held are presented in this paper. Various subsonic inf low treatments are evaluated. Some of these treatments have been found to p roduce reflections at the inflow while others are reflection-free. Results are then presented for the effect of Mach number on the radiated sound. It is shown that as the Mach number increases the source becomes noncompact an d the directivity is characterized by a well-defined peak. By comparing the linear prediction to the experimental results, validity range of linear ap proximation for subsonic jet noise is assessed.