Using Boundary Conditions to Account for Mean Flow Effects in a Zero Mach Number Acoustic Solver

Abstract

The present study is devoted to the modeling of mean flow effects while computing thermoacoustic modes under the zero Mach number assumption. It is first recalled that the acoustic impedance modelling a compressor or a turbine must be pre- scribed under an energetical form instead of the classical acous- tic variables. Then we demonstrate the feasibility to take into ac- count the coupling between acoustic and entropy waves in a zero Mach number framework to capture a family of low frequency entropic modes. The proposed approach relies on a new Delayed Entropy Coupled Boundary Condition (DECBC) and proves able to capture a family of Low frequency entropic mode even though no mean flow term is included into the fluctuating pressure equa- tion.