M. Ihme, M. Breuer

The present study is concerned with the prediction of the radiated sound generated by a turbulent jet. Starting basis was an existing LES code written for the solution of the filtered Navier-Stokes equations for an incompressible fluid. The spatial and temporal discretization are both of second-order accuracy and standard subgrid scale models are applied. Two CAA approaches were taken into account for the prediction of the acoustic far field. The first relies on Lighthills acoustic analogy and uses Greens function to construct an integral formulation of the wave equation. The integration has to be evaluated for each single time step and each far-field point at retarded time leading to a very CPU-time consuming procedure. The second method directly solves the second-order wave equation in the near field by an explicit finite-difference scheme of fourth-order accuracy in space and time putting special emphasis on the accurate representation of the continuous dispersion relation. Owing to a finite acoustic region, appropriate boundary conditions have to be imposed at artificial boundaries. Both first-order accurate and second-order accurate absorbing boundary conditions were applied in the present work. For both CAA methods the acoustic sources given by Lighthills stress tensor were extracted from the LES computation and used as input for the prediction of the acoustic far field. The implementation was verified by different test cases. As a practical application of the hybrid LES/CAA method, the radiated sound of a square eo-flowing jet at low Mach number was considered. The predicted flow and acoustic field were analyzed in detail.

International Workshop on "LES for Acoustics"; Göttingen; 2002

Conference Paper

englisch

A4, 14 Seiten

DGLR-Bericht, 2002, 2002-03, LES for Acoustics - Proceedings; S.1-14; 2002; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

in getr. Zählung;

aeroacoustics, large eddy simulation

Bibliothek

2002