The non‐reflective interface: an innovative forcing technique for computational acoustic hybrid methods

Abstract

Summary The present article concerns a commonly used methodology for the numerical simulation of acoustic emission and propagation phenomena. We consider the so‐called multi‐stage hybrid acoustic approach, in which a given noise problem is simulated via a sequence of weakly coupled computations of noise generation and acoustic propagation stages, wherein the simulation of the propagation stage is based on advanced Computational AeroAcoustics (CAA) techniques. The paper introduces an original forcing technique, namely, the Non‐Reflective Interface (NRI), to enable the transfer of an acoustic signal from an a priori noise generation stage into a CAA‐based acoustic propagation phase. Unlike most existing forcing techniques, the NRI is non‐reflective (or anechoic) in nature and, therefore, can properly handle the backscattering effects arising during the noise propagation stage. This attribute makes the NRI‐based weak‐coupling procedure and the associated CAA‐based hybrid approach compatible with a larger variety of realistic noise problems (such as those involving installed configurations in wind tunnel experiments, for instance). The NRI technique is first validated via several test cases of increasing complexity and is then applied to two aerodynamic noise problems. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

An advanced hybrid method for the acoustic prediction

“…aerodynamic noise). On the same way, all the related outcomes were extensively documented through previous publications, either as journal articles or proceedings of international conferences [22][23][24][25][26][27][28][29][30][31]. The reason for summarizing these various works and associated outcomes here was that, although focusing each on a particular aspect (and deserving each an entire publication in itself), they all targeted the same common objective, which is the development of the advanced CAA-based hybrid approach that the present article is about.…”

“…Thanks to the various methodological outcomes they led to, these studies made it possible to develop an advanced CAA-based hybrid approach, which integrates and connects altogether the diverse aspects of the problem, whilst accounting for their interactions. Such approach was validated through an application to various acoustic problems of increasing complexity [23,24,31] (some of which are presented hereafter).…”

“…With the view of allowing the proper transfer of any given acoustic signal coming from an a priori sound generation stage to within a CAA-based propagation one, an innovative weak coupling approach was recently derived by the present first author [22][23][24]. Such approach relies on the idea of letting the sound generation stage (e.g.…”

“…Within this framework, several dedicated studies were achieved, which all served the same purpose, whilst focusing each on a particular aspect of the problem; besides previous works that led to the development of an optimal CAA method/solver [17,18], a specific research action [22][23][24] consisted in developing a weak coupling approach that could allow a CAA-based propagation stage to be forced with any given acoustic signal whilst offering to handle acoustic backscattering phenomena, for the overall hybrid method is compatible with many situations of interest (cf. the anechoicity requirement evocated above).…”

Numerical Modeling and Investigation on Aerodynamic Noise Characteristics of Pantographs in High‐Speed Trains

“…The direct computation method is called CAA (Computational Aero Acoustics). Viscidity and turbulence effects are simulated accurately through directly solving nonsteady N-S equations and Reynolds average RANS equations [19][20][21]. CAA method requires a numerical solution method with high precision, refined meshes, and nonreflective boundary conditions, so that the computational cost is very high.…”