Determination of acoustic scattering matrices using nonlinear disturbance equations

In this paper, the potential of using nonlinear disturbance equations for the determination of acoustic scattering matrices is investigated. In the course of this the acoustic behavior of a sudden area expansion is analyzed within a multi-step hybrid approach. First, the mean flow solution is determined on the basis of a steady Reynolds averaged Navier-Stokes (RANS) simulation. Then, the acoustic perturbations around this mean flow are computed on a separate mesh by solving the PErturbed Nonconservative Nonlinear Euler (PENNE) equations with a high order time domain solver. Finally the unsteady results are postprocessed with a multi-microphone method in order to extract acoustic scattering matrices over a range of frequencies. The results show that with the proposed set of nonlinear governing equations numerically stable solutions for the determination of acoustic scattering matrices in the time domain are attained. Moreover, comparisons with experimental data demonstrate the reliability and accuracy of the method.