Aeroacoustic Numerical Method Assessment for a Double Stream Nozzle

Abstract

Industrial results obtained from different steady and unsteady numerical and analytical methods for a double stream jet in confluent flow configuration are presented. These results are compared with measurements from anechoic wind tunnel tests of a model nozzle. The test campaign was conducted in the ONERA CEPRA19 facility, and exhaust parameters are representative of take-off, with and without simulated flight effects. During this campaign, in addition to acoustic measurements, LDV (Laser Doppler Velocimetry) technique was used in order to measure steady and unsteady aerodynamic data in several planes downstream the exhaust plane. Those data are used to assess several RANS methods (Reynolds Averaged Navier Stokes - steady calculation) on structured and unstructured 2D meshes using k-e turbulence model. Particularly, the effects of the refinement and of the structure of the mesh, as well as flight effects are investigated. Those data are also used to assess LES method (Large Eddy Simulations - 3D unsteady calculation) performed for the same model nozzle in confluent flow configuration, but without plug. Because results of both steady and unsteady aerodynamic calculations are usually used as inputs of acoustic prediction methods, an assessment of two different aeroacoustic prediction processes is also achieved, with different RANS calculations as input of an improvement of MGB (Mani Gliebe Balsa), and LES calculations as input of an acoustic integral method in the time domain (FfowcsWilliams and Hawkings surface integration). Particularly, flight effects and the ability of the whole aeroacoustic chain to predict them are studied.