Sound and Sources of Sound in a Model Problem with Wake Interaction

Wolf, William; Cavalieri, André V. G.; Backes, Bruno; Morsch-Flho, Edemar; Azevedo, João Luiz F.

doi:10.2514/1.j053713

Cited by 9 publications

(5 citation statements)

References 30 publications

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“…Greschner et al [18], and later Giret et al [19], have pointed out that the quadrupolar sound emitted by a rod airfoil configuration at M = 0.2 was no longer negligible and that the permeable formulation better matched the experimental results of Jacob et al [20] at high frequencies for an integration surface surrounding the whole rod-airfoil system and a portion of its wake. Wolf et al [21], supported by Yu & Lele [22], have shown that in the case of a wake interaction, quadrupolar noise emission was mainly concentrated in the high frequency range. They found that it could be neglected for a Mach number of 0.1, but not for 0.3 and 0.5.…”

Section: Introductionmentioning

confidence: 93%

A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

Hajczak

Sanders

Vincent

et al. 2021

Journal of Sound and Vibration

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This work is a contribution to the ongoing debate about the role of quadrupoles in low Mach number flows, studied through the use of solid and permeable surface Ffowcs-Williams & Hawkings (FW-H) integrals for landing gear numerical noise predictions. It rests upon the key idea that the dominance of surface sources over volume sources can only be guaranteed when the compact-source condition is met. We propose here to express this property as a condition on the smallness of the product between the Mach and Strouhal numbers, or formally as MSt < 1. We consider a canonical isolated wheel, that basically consists in a shallow circular cavity inscribed in a coin-like cylinder, thus presenting few different length scales, as compared to a full landing gear assembly. Zonal Detached Eddy Simulations are performed on several gradually refined grids to assess the grid convergence of the numerical result. In particular, important computational effort is put into the accurate resolution of acoustic waves up to Strouhal numbers such that MSt > 1. Overall, determining the real significance of quadrupoles was challenging as numerical errors or misleading effects such as near-field terms, surface discretization, or source domain truncation biased the initial permeable surface results. Even when these sources of bias are removed, non-negligible differences are found between the solid and permeable noise spectra at non-compact St values, while both formulations are equivalent at lower Strouhal numbers. The analysis of these differences is extended to the determination of their impact on frequency-domain noise maps obtained with the DAMAS algorithm fed with far-field signals computed with both FW-H approaches. A tentative interpretation of the wheel noise sources is finally proposed, highlighting the dominant role of the scattering of aerodynamic sources by the cavity downstream edge at low Strouhal numbers, while wake sources dominate at higher Strouhal numbers.

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Section: Introductionmentioning

confidence: 93%

A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

Hajczak

Sanders

Vincent

et al. 2021

Journal of Sound and Vibration

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“…For those applications where quadrupoles are relevant (see, for instance, the studies on the noise radiated by wakes of subsonic flows by Wolf et al [53,54]), Di Francescantonio [55] proposed changing f to a permeable moving surface moving at a velocity v i = 0 that encloses all the volumetric sources producing non-negligible noise instead of using the body surface. Equation (7) can then be rearranged to include the terms accounting for the evaluation of the noise sources in the permeable surface:…”

Section: Far-field Noise Predictionmentioning

confidence: 99%

Hybrid Computation of the Aerodynamic Noise Radiated by the Wake of a Subsonic Cylinder

Eiximeno,

Tur-Mongé,

Lehmkuhl

et al. 2023

Fluids

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The noise radiated by the flow around a cylinder in the subcritical regime at ReD=1×104 and at a subsonic Mach number of M=0.5 is here studied. The aerodynamic sound radiated by a cylinder has been studied with a wide range of Reynolds numbers, but there are no studies about how the Mach number affects the acoustic field in the subsonic regime. The flow field is resolved by means of large-eddy simulations of the compressible Navier–Stokes equations. For the study of the noise propagation, formulation 1C of the Ffowcs Williams–Hawkings analogy is used. The fluid flow results show good agreement when comparing the surface pressure coefficient, the recirculation length, the vortex shedding frequency and the force coefficients against other studies performed under similar conditions. The dynamic mode decomposition of the pressure fluctuations is used to relate them with the far-field noise. It is shown that, in contrast to what happens for low Mach numbers, quadrupoles have a significant impact mainly in the observers located in the streamwise direction. This effect leads to a global monopole directivity pattern as the shear fluctuations compensate for the lower value of the aeolian tone away from the cross-stream direction.

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“…In this study, we use compressible direct numerical simulations (DNS) in a generalized curvilinear coordinate and conservative form (Wolf et al. 2015). The numerical method uses a sixth-order compact scheme implemented on a staggered grid for spatial discretization (Nagarajan, Lele & Ferziger 2003).…”

Section: Numerical Simulationmentioning

confidence: 99%

On the emergence of secondary tones in airfoil noise

et al. 2023

Self Cite

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We present the results of direct numerical simulations of a NACA 0012 airfoil, with Mach number 0.3 and angle of attack of $3^\circ$ , examining the dynamics of the flow with increasing Reynolds numbers. Two-dimensional simulation results are obtained with chord-based Reynolds numbers in the range $3.2 \times 10^3 \leq Re \leq 2.70 \times 10^4$ , where each simulation uses the last time step of the previous one as a starting point, to capture the evolution of dynamics as a function of $Re$ . The development of the pressure fluctuations with time shows a transition from periodic to quasi-periodic attractor for $2.38 \times 10^4 \leq Re \leq 2.42 \times 10^4$ , leading to the emergence of secondary tones in the wall and acoustic field pressure spectra, different from peaks related to the fundamental frequency $f_1$ and the respective harmonics; a second, incommensurate frequency $f_2$ appears, leading to several secondary tones with frequency $af_1 + bf_2$ , with $a$ and $b$ integers. Further increase of the Reynolds number leads to the emergence of a tertiary frequency, $f_3$ , indicating a route to chaos of the Ruelle–Takens–Newhouse type. Such a mechanism is related to the ladder-type characteristic structure of the tones, indicating that dynamic systems theory is an important tool for understanding airfoil tonal noise.

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Sound and Sources of Sound in a Model Problem with Wake Interaction

Cited by 9 publications

References 30 publications

A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

Hybrid Computation of the Aerodynamic Noise Radiated by the Wake of a Subsonic Cylinder

On the emergence of secondary tones in airfoil noise

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