Jet Noise Prediction with Eddy Relaxation Source Model

摘要

Previously, a hybrid CFD/CAA approach has been applied for jet noise prediction utilizing a stochastic realization of the Tarn &c Auriault (T&A) and the Tarn, Pastouchenko and Viswanathan (TPV) source models. These models describe two-point cross-correlation functions of a mixing noise source in the jet shear-layer. All input data needed for the modeling can be derived from RANS. The fluctuating acoustic sources are generated stochastically by the Fast Random Particle-Mesh (FRPM) method. For sound propagation a CAA code PIANO is applied with linearized or non-linearized Euler equations in perturbed form. In comparison to measurements, CAA results with the T&A and TPV source models have proven a relatively high accuracy for jet mixing noise prediction of different isolated nozzle configurations (single/dual stream jets, static and forward-flight configuration, hot/cold). On the other hand, recent studies of the authors reveal that alternative source models based on vorticity modeling deliver better noise predictions for the noise generation mechanisms underlying airframe noise problems, i.e. trailing or leading edge noise. Both modeling approaches are well applicable if mixing and airframe noise are regarded separately. However, for instance the study of jet installation effects, where the jet interacts with the trailing edge of an airfoil, require a combination of jet mixing and airframe noise prediction. A common base for both source mechanisms of installed configurations could be provided by the recently proposed Eddy Relaxation source model, which is used to force stochastically the vortical structures in the source region. Based on the relaxation source parameter the coupling can be achieved with variable strength, ranging from entirely prescribed sources to unforced simulation. Two different configurations (single stream jet and jet-flap interaction) in 2-D and 3-D space are currently studied with the eddy relaxation source model. First test computations of these configurations have been performed, which delivered encouraging results.