Investigation of the Acoustic Boundary Conditions Used for the Entropy Wave Generator Test Case

The Entropy Wave Generator (EWG) experiment is a generic test case for indirect combustion noise. This test case has been studied extensively by means of experimental, analytical and numerical methods. Numerical and analytical studies show the major importance of modelling the acoustic boundary conditions to obtain accurate results. So far, Navier-Stokes Characteristic Boundary Conditions (NSCBC) have been used to model the impedance for CFD simulations. Within this paper, di erent proposals for setting up the NSCBC are reviewd. Furthermore, the modelling of the downstream impedance is enhanced by applying time domain impedance boundary conditions (TDIBC).