Jet noise analysis using an efficient LES/high-order acoustic coupling method

The use of a CFD/CAA method, where fluctuations are extracted on a surface and propagated analytically to the far-field, is becoming a practical approach for industrial jet noise prediction. However, the placement of the surface can be problematic and a source of error, so here an efficient LES/APE coupling method that relies on volumetric sources is utilised. This allows the use of an existing, well validated and robust finite volume LES code to compute the unsteady flow, from which the volumetric sources are extracted, to then compute the propagation of the acoustic waves to the far-field using a high-order finite element APE code with a grid more appropriate for this task. Furthermore, this coupled methodology allows the studying of noise propagation in complex configurations in which the use of surface integral methods could be challenging. In this work, a coupling strategy is used in which all the necessary data is exchanged directly via the high-speed communication network using an open-source library. The efficiency of the parallel-coupling strategy is demonstrated by applying it to a 2D canonical case and comparing it with an existing file-based approach. For the acoustic propagation, the APE solver used is called AcousticSolver, part of the high-order spectral/hp finite element open-source code Nektar++. The present LES/APE framework is fist validated for 3D jet applications by studying the noise propagation of a low-Reynolds number case. Then the method is applied to a more realistic high Reynolds number jet obtaining encouraging results in terms of flow and acoustic predictions.