Additional terms for the use of Ffowcs Williams and Hawkings surface integrals in turbulent flows

Rahier, Gilles; Huet, Maxime; Prieur, Jean

doi:10.1016/j.compfluid.2015.07.014

Cited by 54 publications

(35 citation statements)

References 32 publications

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“…Such a situation has been described, for instance, by Ianniello et al who considered the noise originating from vortices in the wake of a non-cavitating marine propeller [67]. This stresses the importance of searching for viable alternatives to using open FW-H control surfaces, such as the ones discussed by Rahier et al [51] or Sinayoko et al [68]. An intermediate option would be to solve the volume integral in the wake region only and neglecting it further away where quadrupole sources may be expected to be negligible.…”

Section: Discussionmentioning

confidence: 93%

“…Moreover, each of the control surfaces was also evaluated in an open-ended variant in order to study how much spurious noise the turbulent structures penetrating the downstream-most extents will generate. This phenomenon has been described, for instance, by Rahier et al in the context of jet noise [51], and is caused by the noise sources leaving the control surface and not being accounted for using the volume integral which has been neglected.…”

Section: Acoustic Analysismentioning

confidence: 99%

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Characterisation of sheet cavity noise of a hydrofoil using the Ffowcs Williams–Hawkings acoustic analogy

2016

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Concerns about pollution of the marine environment with ship-induced noise and the scarcity of available numerical methods have recently stimulated significant amounts of research in hydroacoustic modelling. In this work, Large Eddy Simulation (LES) is used with Schnerr-Sauer mass-transfer cavitation model and a porous Ffowcs WilliamsHawkings (FW-H) acoustic analogy in order to simulate sheet cavitation on a NACA0009 hydrofoil. The aim is to investigate how well the proposed method captures the dominant noise sources associated with periodic sheet cavitation. The study further focuses on practical aspects, such as the importance of the non-linear FW-H term and convergence of the acoustic solution depending on the choice of the integration surface. This is done by correlating the radiated noise with integral and local flow quantities, such as cavity volume, lift coefficient and local vapour content. A key finding of the study is that the simulation framework is capable of correctly capturing the monopole nature of the sound generated by an oscillating cavity sheet. Results indicate that the numerical method is incapable of accurately resolving the flow during the final collapse stages of smaller cavity clouds, mainly due to mesh density limitations and the use of an incompressible flow assumption. Lack of small-scale bubble structures also causes the high-frequency range of the noise spectra to be under-predicted. Despite certain limitations the presented method offers a significant insight into the nature of cavitation-dominated noise and allows for some of the dominant sound generating mechanisms to be categorised.

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Section: Discussionmentioning

confidence: 93%

Section: Acoustic Analysismentioning

confidence: 99%

Characterisation of sheet cavity noise of a hydrofoil using the Ffowcs Williams–Hawkings acoustic analogy

2016

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“…[28] provided insight to the additional terms for the use of FW-H surface integrals. The study specified the links between the surface and volume integrals.…”

Section: The Original Fw-h Equation Was Developed In 1969 Frommentioning

confidence: 99%

Prediction of Horizontal Axis Wind Turbine Acoustics

Kurultay¹,

Alpman²

2016

Marmara Fen Bil Dergisi

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Wind power industry has been a growing market and maturing technology for several decades. Increasing wind power generation necessitates closer installation of wind turbines to people and their residences. For that reason, wind turbine noise becomes a serious and controversial phenomenon and it is anticipated to become more stringent issue while wind power generation is increased recently. The aim of this study was to propose a methodology to predict the wind turbine blade noise by using two dimensional blade section flows and noise analysis/simulation and combining the noise sources to evaluate the total blade noise with reasonable accuracy.Within the scope of this work, the purpose was to perform a two dimensional flow and noise simulation for the two bladed NREL Phase VI wind turbine with the aid of a commercially available Computational Fluid Dynamics (CFD) software ANSYS-FLUENT by using User Defined Functions after applying some corrections under certain assumptions. Analysis results were compared with the 12% scaled model of NREL Phase VI wind turbine acoustic noise measurements conducted in In Korea Aerospace Research Institute (KARI) at the low speed wind tunnel. Blade noise of the measurements were compared with the analysis results at different wind speeds of 5.4 m/s, 7.4 m/s, 12.3 m/s, and 13.3 m/s. For the tip region and inboard area of the blade, reasonable agreement was achieved at certain wind speeds. Additionally, the summation of the contribution from the each blade section was used to predict the total noise emission.

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“…Underestimations are found for low frequencies St ≤ 0.1 and a slight overestimation for angles ≥90° for frequencies St ≥ 1. In [30], Rahier et al proposed additional surface terms in order to reduce the spurious noise generated in aeroacoustic computations by the flow turbulence passing through a Ffowcs Williams and Hawkings (FW-H) control surface. This spurious noise is due to the fact that some volume sources are not taken into account in the calculations limited by surface integrations.…”

Section: Far Field Pressurementioning

confidence: 99%

“…Due to the spurious noise generated in aeroacoustics computations by the flow turbulence passing through a control surface, additional surface terms proposed by Rahier [30] are added in order to reduce this spurious noise. The results using different configurations of the control surface together with these additional surface terms is analyzed in the present paper.…”

Section: Acoustic Computationmentioning

confidence: 99%