Vortical–acoustic resonance in an acoustic resonator: Strouhal number variation, destabilization and stabilization

Dai, Xiwen

doi:10.1017/jfm.2021.415

Cited by 2 publications

(2 citation statements)

References 76 publications

(186 reference statements)

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“…Comprehensive reviews of the literature can be found in and Hsu et al (2016). Studies have demonstrated significant influences of TMs and slightly LMs on vortex structures (Peters 1993;Tonon et al 2011), on flow instabilities (Yamouni, Sipp & Jacquin 2013;Towne et al 2017;Martini, Cavalieri & Jordan 2019;Dai 2021b) and on wave scattering (Bennetts, Peter & Craster 2018;Bobinski et al 2018;Zheng, Porter & Greaves 2020). This study, however, still focuses on the TM phenomenon itself (Callan, Linton & Evans 1991;Duan et al 2007;Hein, Koch & Nannen 2012;Newman 2018).…”

Section: Introductionmentioning

confidence: 99%

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Commonality and difference in the eigenfunctions of various types of acoustic trapped modes

Dai

2024

J. Fluid Mech.

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We investigate and compare various types of acoustic trapped modes (TMs) in resonator–waveguide systems. The goal is to understand the commonality and difference between the mechanisms of common (symmetry protected, invisibility protected and symmetry–periodicity protected) and accidental TMs, occurring continuously and discretely in the resonator length–frequency two-parameter space. The latter type cannot yet be explained via an operator decomposition. Here, all TMs are explained in the same way by analysing why and how the propagating-wave loops in the eigenfunctions can satisfy the eigenmode condition (loop magnitude and phase constraints for closure) and the wave-trapping condition (loop zero-radiation condition) simultaneously. Firstly, the unified analysis reveals the commonality that one or multiple coupled propagating-wave loops satisfy TM conditions, and the difference. In common TMs, the loop zero radiation is independent of the single loop phase constraint that selects the TM frequency as a continuous function of resonator length. On the other hand, loop zero radiation in accidental TMs depends on the loop phase constraints and there are two phase constraints. Only at the crossing points of the two phase constraints can zero-radiation loops be ensured. Secondly, in contrast to previous studies, it suggests that modal degeneracy, avoided crossing and resonance-width bifurcation are not the mechanisms of accidental TMs.

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Section: Introductionmentioning

confidence: 99%

“…2011), on flow instabilities (Yamouni, Sipp & Jacquin 2013; Towne et al. 2017; Martini, Cavalieri & Jordan 2019; Dai 2021 b ) and on wave scattering (Bennetts, Peter & Craster 2018; Bobinski et al. 2018; Zheng, Porter & Greaves 2020).…”

Section: Introductionmentioning

confidence: 99%

Commonality and difference in the eigenfunctions of various types of acoustic trapped modes

Dai

2024

J. Fluid Mech.

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Self-sustained azimuthal aeroacoustic modes. Part 1. Symmetry breaking of the mean flow by spinning waves

Faure-Beaulieu,

Xiong,

Pedergnana

et al. 2023

J. Fluid Mech.

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In this paper, we study the aeroacoustic instability which occurs in a deep axisymmetric cavity in a turbulent pipe flow. This phenomenon is the axisymmetric counterpart of the classical whistling of a rectangular deep cavity subject to a grazing flow. The whistling of such axisymmetric cavity originates from the interaction of the coherent fluctuations of the vorticity at the cavity's opening with one of its trapped azimuthal or radial acoustic modes. We focus here on the situation involving the first pure azimuthal mode, which is trapped in the cavity. As a consequence of the rotational symmetry of the configuration, azimuthal modes are actually pairs of degenerate eigenmodes, or almost degenerate in the presence of small asymmetries. Therefore, the aeroacoustic instabilities exhibit more complex mechanisms than in the case of a rectangular deep cavity. In particular, we show that self-sustained spinning modes induce a symmetry breaking of the mean flow and we will elucidate the details of this phenomenon. To that end, simultaneous acoustic and time-resolved stereoscopic particle image velocimetry (PIV) measurements are performed. They reveal that when large-amplitude aeroacoustic waves spin around the cavity, a quasi-steady mean flow starts whirling slowly in the opposite direction to the wave propagation. A linear perturbation analysis around an axisymmetric mean flow confirms the experimental observations: although the incoming pipe flow is not swirling, the hydrodynamic component of the aeroacoustic wave induces such whirling motion of the mean flow because of the forcing from the steady part of the coherent Reynolds stress tensor.

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Vortical–acoustic resonance in an acoustic resonator: Strouhal number variation, destabilization and stabilization

Abstract: Abstract

Cited by 2 publications

References 76 publications

Commonality and difference in the eigenfunctions of various types of acoustic trapped modes

Commonality and difference in the eigenfunctions of various types of acoustic trapped modes

Self-sustained azimuthal aeroacoustic modes. Part 1. Symmetry breaking of the mean flow by spinning waves

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