Hybrid Aeroacoustic Computations: State of Art and New Achievements

Abstract

This paper collects the state of the art and the tremendous progress that has been made in hybrid modeling of aeroacoustic sound. Hybrid modeling is defined such that flow and acoustics are modeled separate and connected by an aeroacoustic model. The contributions will be classified with respect to the aeroacoustic models being developed, covering Lighthill’s analogy, Ffowcs Williams and Hawkings, vortex sound, linearized Euler equations (LEE), and different perturbation equations modeling flow induced sound. Within each topic, specific applications, such as jet noise, aircraft noise, ground mobility, noise, fan noise and human phonation, are covered. We focus on the accomplishments and provide the authors’ contribution to aeroacoustic research. Eventually, a concise summary of the different methods and their capabilities is included.

Efficient numerical simulation of the human voice

“…simVoice is based on the hybrid aeroacoustic approach which decomposes the task of sound computation into a flow computation and an acoustic propagation simulation [35]. For the latter part, the aeroacoustic source terms depending on the partial differential equation (PDE) governing the acoustic field (such as Lighthill acoustic analogy, acoustic perturbation equations, etc.)…”

Flexible Discretization for Computational Aeroacoustics

“…For the acoustic computation performed by openCFS [11], Lighthill's aeroacoustic analogy for low Mach numbers is applied (for details, we refer to [10]). In doing so, the source term fitting to the wave equation 1and assuming just sources in the subdomain Ω 1 computes by…”

Helmholtz’s decomposition for compressible flows and its application to computational aeroacoustics

“…Every method tries to overcome the challenges of effective and accurate computation of the radiated sound. Two important difficulties, which have to be considered for the simulation of flow sound problems, are summarized as [1,2,4]: 1. Energy disparity and acoustic inefficiency: A large disparity between the flow energy and the radiated acoustic energy of flow-induced sound has been observed.…”

“…This implies that direct simulation of flow and sound must be able to resolve very different scales and amplitudes. For low Mach number applications, one solution is to use a hybrid aeroacoustic workflow [4]. 2.…”

“…This implies that an acoustics simulation has different requirements for the discretization and for the relevant domain size, to fit several wavelength. For low Mach number applications, one efficient simulation solution is to decouple flow and acoustics by a hybrid workflow [4].…”