Aeroacoustic wave equation based on Pierce's operator applied to the sound generated by a mixing layer

Schoder, Stefan; Spieser, Étienne; Vincent, Hugo; Bogey, Christophe; Bailly, Christophe

doi:10.2514/6.2022-2896

Cited by 10 publications

(17 citation statements)

References 39 publications

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“…4) [56,57], is largely applicable also in the present complex separated flow. The impact of this cancellation, which has also been reported for mixing layer sound generation in [58], on the resulting acoustic field of the present configuration will be illustrated in the analysis below.…”

Section: Source Term Analysissupporting

confidence: 57%

Aeroacoustic formulations for confined flows based on incompressible flow data

et al. 2022

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The hybrid aeroacoustic approach is an efficient way to address the issue of the disparity of scales in Computational AeroAcoustics (CAA) at low Mach numbers. In the present paper, three wave equations governing propagation of flow-induced sound of low Mach number flows, namely the Perturbed Convective Wave Equation (PCWE), Ribner’s Dilatation (RIB) equation, and Lighthill’s wave equation, are applied using the Finite Element Method (FEM). An airflow through a circular pipe with a half-moon-shaped orifice at three operating flow speeds is considered, where validation data from measurements on a dedicated test rig is available. An extensive analysis of the flow field is provided based on the results of the incompressible flow simulation. The resulting acoustic source terms are investigated, and the relevant source term contributions are determined. The results of the acoustic propagation simulations revealed that the PCWE and RIB are best suited for the present task. The overall deviation of the predicted pressure spectra from the measured mean values amounted to 2.26 and 2.13 times the standard deviation of the measurement compared to 3.55 for Lighthill’s wave equation. Besides reliably predicting the flow-induced sound, the numerical procedure of source term computation is straightforward for PCWE and RIB, where the source term contributions, shown to be relevant, solely consist of time derivatives of the incompressible pressure. In contrast, the Lighthill source term involves spatial derivatives and, thus, is strongly dependent on the spatial resolution and the numerical method actually used for approximating these terms.

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Section: Source Term Analysissupporting

confidence: 57%

Aeroacoustic formulations for confined flows based on incompressible flow data

et al. 2022

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“…Our research resolved barrier 2 for incompressible flows (see Fig. AWE-PO source compared to Lighthill's source [36,38]. For the first time, this reduction was…”

Section: Barriermentioning

confidence: 68%

“…For example, one achieves reasonable results when solving Lighthill's equation with appropriate boundary conditions [108,123], especially for a low Mach number approximation of the source term [170,151,152,165,87,171,119]. Figure 1.4b shows the fluctuating pressure obtained from Lighthill's equation for the mixing layer example [36,38].…”

Section: The Challengementioning

confidence: 99%

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Computational aeroacoustics of the EAA benchmark case of an axial fan

Schoder

Junger

2020

Acta Acust.

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This contribution benchmarks the aeroacoustic workflow of the perturbed convective wave equation and the Ffowcs Williams and Hawkings analogy in Farassat’s 1A version for a low-pressure axial fan. Thereby, we focus on the turbulence modeling of the flow simulation and mesh convergence concerning the complete aeroacoustic workflow. During the validation, good agreement has been found with the efficiency, the wall pressure sensor signals, and the mean velocity profiles in the duct. The analysis of the source term structures shows a strong correlation to the sound pressure spectrum. Finally, both acoustic sound propagation models are compared to the measured sound field data.

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“…Thereby, we assume to use a convex evaluation domain. With this assumption, the scalar potential formulation of the decomposition is valid and beneficial [12]. Theorem 3.1 (Helmholtz decomposition for finite domains) Every square integrable vector field u ∈ [L 2 (Ω)] 3 , C 1 smooth, on a simply connected, Lipschitz domain Ω ⊆ R 3 , has an L 2 -orthogonal decomposition…”

Section: Formulationmentioning

confidence: 99%

Helmholtz's decomposition for Aeroacoustics using a standard Flow Solver

Schoder¹

2022

Preprint

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This paper is a short guideline to the decomposition of a compressible velocity into vortical and compressible structures using standard flow solvers. In particular, this is a fast solution to get an idea of the compressible fields inside your simulation, respectively acoustics for low Mach number isothermal flows. The details of the implementation are presented and the algorithm is applied to an overflown cavity with a lip. The results of the flow solver show clearly visible to acoustic radiation for the application. Finally and as previous studies showed, the use of the scalar potential formulation of Helmholtz's decomposition is valid for convex propagation domains.

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Aeroacoustic wave equation based on Pierce's operator applied to the sound generated by a mixing layer

Cited by 10 publications

References 39 publications

Aeroacoustic formulations for confined flows based on incompressible flow data

Aeroacoustic formulations for confined flows based on incompressible flow data

Computational aeroacoustics of the EAA benchmark case of an axial fan

Helmholtz's decomposition for Aeroacoustics using a standard Flow Solver

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