A frequency domain linearized Navier–Stokes method including acoustic damping by eddy viscosity using RANS

Holmberg, Andreas; Kierkegaard, Amelie; Weng, Chenyang

doi:10.1016/j.jsv.2015.02.030

Cited by 30 publications

(23 citation statements)

References 22 publications

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“…Assuming also that turbulence fluctuations do not generate significant density variations, i.e. ρ ′ = 0, as in previous studies [49,50], we can prove that the density-weighted variables given by Eq. ( 12) simplify to the variables defined in Eq.…”

Section: Uncoupled Formulationsupporting

confidence: 82%

“…This expression is the generalisation of previous work [47,49,50] to include entropy fluctuations. For low-Mach-number flows, variations of the mean density ρ are negligible.…”

Section: Uncoupled Formulationmentioning

confidence: 55%

“…The latter assumption is justified owe to the low Mach number of the configurations of interest. The first simplification was relaxed by [49,50] by decomposing the flow variables into mean, coherent and, turbulent parts (the so-called triple decomposition) as proposed by Reynolds and Hussain [51]. Additionally, some authors have considered the energy equation for laminar flows, e.g.…”

Section: Introductionmentioning

confidence: 99%

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On the scattering of entropy waves at sudden area expansions

Guzmán-Iñigo,

Yang,

Gaudron

et al. 2021

Preprint

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In this work, we investigate both numerically and theoretically the sound generated by entropy waves passing through sudden area expansions. This is a canonical configuration representing internal flows with flow separation and stagnation pressure losses. The numerical approach is based on a triple decomposition of the flow variables into a steady mean, a small-amplitude coherent part, and a stochastic turbulent part. The coherent part contains acoustic, vortical, and entropy waves. The mean flow is obtained as the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations. The equations governing the coherent perturbations are linearised and solved in the frequency domain. To account for the effect of turbulence on the coherent perturbations, a frozen eddy viscosity model is employed. When entropy fluctuations pass through the area expansion, the generated entropy noise behaves as a low-pass filter. The numerical predictions of the noise at low frequencies are compared to the predictions of compact, quasi-one-dimensional, and isentropic theory and large discrepancies are observed. An alternative model for the generated entropy noise tailored for area expansions is then proposed. Such model is based on the conservation of mass, momentum, and energy written in integral form. The model assumes zero frequency and the one-dimensionality of the flow variables far upstream and downstream of the expansion. The predictions of this model agree well with the numerical simulations across a range of finite subsonic Mach numbers including low, intermediate, and high Mach numbers. The contributions of this work are both numerical and theoretical. Numerically, a triple decomposition adapted to high-Mach-number, compressible flows is introduced for the first time in the context of acoustic simulations. From a theoretical point of view, the model proposed here represents the first quasi-steady model that captures correctly the low-frequency entropy noise generated at sudden area expansions, including at high subsonic Mach numbers.

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Section: Uncoupled Formulationsupporting

confidence: 82%

“…This expression is the generalisation of previous work [47,49,50] to include entropy fluctuations. For low-Mach-number flows, variations of the mean density ρ are negligible.…”

Section: Uncoupled Formulationmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

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On the scattering of entropy waves at sudden area expansions

Guzmán-Iñigo,

Yang,

Gaudron

et al. 2021

Preprint

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“…The methodology is independent of the reflection properties of the upstream and downstream duct terminations, allowing a direct comparison between numerical and experimental data. Even in presence of non-linear phenomena in the aeroacoustic field, the N-port methodology has been used to predict the whistling frequency of T-junctions [13,14] and orifices [5,27], applying the acoustic energy criterion based on the scattering matrix formulation [8].…”

Section: Acoustic Characterization Two-port Methodsmentioning

confidence: 99%

“…As discussed in [1,10,13] the aeroacoustic instabilities develop from a linear state to a non-linear regime as the damping mechanisms of vortex shedding become significant for the saturation of the shear layer response. Numerical methods based on linearized Navier-Stokes (LNS) equations can therefore be applied to predict the onset of aeroacoustic instabilities in T-junctions [14], orifices [7] or Helmholtz resonators [15]. The non-linear aeroacoustic interactions can be modeled using scale-resolving methods such as direct numerical simulations (DNS) [16], and large-eddy simulations (LES) [9,11].…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic instability analysis of a Helmholtz resonator using a High-Order DG Solver based on URANS equations

Criscuolo

Renac²,

Couaillier³

et al. 2020

Aiaa Aviation 2020 Forum

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This paper presents an analysis of the aeroacoustic instabilities in a slit-type Helmholtz resonator subjected to a low Mach number grazing flow. This configuration can be susceptible to non-linear feedback phenomena due to the interaction between the hydrodynamic and acoustic field in the orifice proximity. The aeroacoustic flow field is simulated by solving the 2D unsteady Reynolds averaged Navier-Stokes (URANS) equations using a high-order discontinuous Galerkin (DG) solver. The response of the Helmholtz resonator to an incident acoustic field is analyzed using a two-port characterization technique. The onset of the aeroacoustic instabilities is investigated by applying an acoustic energy criterion based on the scattering matrix formulation. The numerical results are compared to experimental data obtained in a measurement campaign carried out at the KU Leuven test facility. The comparison between the numerical and experimental data demonstrates a very good agreement, highlighting the potential of the applied numerical approach for the aeroacoustic instabilities investigation.

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