Numerical Analysis of Indirect Combustion Noise Generation Within a Subsonic Nozzle

Abstract

Indirect noise is analyzed by numerical simulations of the Entropy Wave Generator experiment, which has been set up to study the fundamental mechanism of indirect combustion noise generation. Previous studies of this test case show the major importance of modeling the impedance terminations of the test rig to obtain accurate results. So far, characteristic boundary conditions have been used to model the impedance for numerical calculations. Within this paper, different proposals for setting up the characteristic boundary conditions are reviewed. In addition, a higher accuracy of the impedance model is achieved by applying time-domain impedance boundary conditions. As part of the Entropy Wave Generator experiment, indirect noise is generated by electrical heating wires. It has been found in this study that the modeling of these heat sources is crucial for obtaining accurate results. An advanced heat source model is proposed that is in excellent agreement with the experimental data. Both the advanced impedance and heat source model account for a better agreement between experimental and numerical data than reported in literature to date.