Direct aeroacoustic simulation of acoustic feedback phenomena on a side-view mirror.pdfVIP

Journal of Sound and Vibration 371 (2016) 132–149 Contents lists available at ScienceDirect Journal of Sound and Vibration journal homepage: /locate/jsvi Direct aeroacoustic simulation of acoustic feedback phenomena on a side-view mirror Hannes M. Frank n, Claus-Dieter Munz Institute for Aerodynamics and Gasdynamics, University of Stuttgart, Pfaffenwaldring 21, 70550 Stuttgart, Germany article info Article history: Received 16 October 2015 Received in revised form 1 February 2016 Accepted 5 February 2016 Handling Editor: J. Astley Available online 22 February 2016 Keywords: Aeroacoustics Large Eddy Simulation Side-view mirror Tonal noise Aeroacoustic feedback loop Direct noise computation High order method Discontinuous Galerkin Spectral elements Compressible Navier-Stokes equations Laminar separation Global instability abstract The ?ow around a side-view mirror and its noise generation are investigated using large eddy simulation and direct acoustic simulation. To this end, we use the high order discontinuous Galerkin spectral element method on non-conforming curved elements. Tonal noise is observed, which originates at the trailing edge downstream of laminar separation, coinciding with experimental results. In order to determine the nature of the tonal noise generation mechanism, we perform a linear stability analysis and employ a global perturbation approach in combination with dynamic mode decomposition. The perturbation analysis based on the whole ?ow ?eld demonstrates the existence of a global instability involving convective disturbance growth, acoustic scattering at the trailing edge and acoustic receptivity at a rounded edge slightly upstream of separation. The results clearly show the tonal noise to be caused by the so-called acoustic feedback loop known from airfoil aeroacoustics. This phenomenon has been simulated here for the ?rst time for a complex geometry. 2016 Elsevier Ltd. All rights reserved. 1. Introduction Among other industries, automotive man