Wave Number Frequency Spectra of a Lifting Wake for Broadband Noise Prediction

Devenport, William J.; Wenger, Christian W.; Glegg, Stewart; Miranda, Joseph A.

doi:10.2514/2.462

Cited by 9 publications

(3 citation statements)

References 8 publications

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“…Beyond the presentation mentioned taken from Blake, 3 this length scale is also defined and used in works by Amiet, 4 Wygnanski et al, 5 and Glegg. 6 It has been examined recently in much closer detail by Devenport et al 7,8 and Glegg et al 9 In papers such as these, the length scales in question were usually determined in one of three basic ways. First, scales could be determined using an exhaustive array of two-point velocity correlation measurements.…”

Section: Derivation Of Integral Correlation Length Scalesmentioning

confidence: 99%

Turbulence Correlation Length-Scale Relationships for the Prediction of Aeroacoustic Response

2005

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Expressions to describe the correlation length scales of turbulent inflow to an aerodynamic body are derived as functions of the classic integral length scale and anisotropy correction factors. These one-point parameters are significantly easier to determine experimentally than traditional correlation-scale measurement techniques, which involve multiple probes at multiple locations. As such correlation scales are necessary to properly estimate the aeroacoustic response of the body, such a technique could have substantial benefit in a wide variety of applications. The approach is applied to a recent experimental study examining the response of a stator downstream of a propeller that is itself ingesting broadband turbulence. Results suggest that the derived expressions not only accurately represent correlation length scales, but also enable the accurate prediction of the acoustic output of the stator. Nomenclaturevector of quantity i i 1 = quantity i in the freestream direction i 2 = quantity i in the direction normal to airfoil (stator) surface i 3 = quantity i in the spanwise direction of airfoil (stator) surface i ∞ = freestream quantity i * = complex conjugate of quantity i k = wave number L i = geometric length scale M = Mach number q = dynamic pressure R i j = correlation function between turbulent velocity components u i and u j r = separation distance between two points Se = aerodynamic response function (Sears function) U = mean velocity component u = turbulent velocity component x = flow location (position) α c , β c = anisotropy scaling factors β = angle between acoustic source and receiver, measured with respect to dipole axis γ 2 = coherence function δ = Dirac delta function , 1 = classic turbulence integral length scale i | j = turbulence correlation scale of jth component of velocity in ith direction ρ 0 = density of fluid ii = autopower spectrum in the ith direction ii (r) = cross-power spectrum in the ith direction (separated by distance r)p rad = radiated far-field acoustic pressure φ ii (r) = nondimensional cross-spectral density function of turbulence in the ith direction (separated by distance r) ω = gust or event frequency (=2π f )

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Section: Derivation Of Integral Correlation Length Scalesmentioning

confidence: 99%

Turbulence Correlation Length-Scale Relationships for the Prediction of Aeroacoustic Response

2005

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“…In any case, it is the upwash turbulence spectrum (i.e. in y-direction) that is required to assess the potential interaction-noise of the wake with a downstream stator vane or airfoil 40 . This is not yet available from the current data and is part of an ongoing study.…”

Section: Wake Flow Measurementsmentioning

confidence: 99%

Concept, design and characterization of a small aeroacoustic wind tunnel facility with application to airfoil measurements

Winkler¹,

Carolus²

2009

Noise Control Eng. J.

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Experimental investigation of flow-induced sound and sources of soundnecessitates an adequate environment of low interfering noise and suppression of unwanted sources of sound. In order to investigate the sound from fluidstructure interactions, a low-noise wind tunnel has been designed and implemented. This paper gives an overview of the design criteria and specifications, along with an aeroacoustic and aerodynamic characterization of the facility. The suitability to airfoil self-noise studies is explored and first measurements with a model airfoil are presented. The paper concludes with an outlook on future applications. © 2009 Institute of Noise Control Engineering.

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“…Because this information is not generally available, the turbulence is usually assumed to behave as though it were homogeneousand isotropic, and von Kármán's interpolation formula or a similar function is used. In fact, the upwash correlation function in wake ows is quite different from that implied by von Kármán's interpolation; for example, see Devenport et al, 3 Wittmer et al, 4 and Wenger et al 5 It is dominated by the anisotropyand inhomogeneityvisiblein the mean ow and its expression in the large-eddy structure of the turbulence. Devenport et al 3 show that these differences can have a signi cant effect on the broadband noise generated.…”

Section: Introductionmentioning

confidence: 97%

Two-Point Descriptions of Wake Turbulence with Application to Noise Prediction

Devenport

Muthanna

et al. 2001

AIAA Journal

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Measurements of the four-dimensional two-point correlation tensor of a fully developed airfoil wake are presented. These data allow examination of the characteristic eddies of the turbulence through proper orthogonal decomposition and linear stochastic estimation. A simple generic technique has been developed to extrapolate the correlation tensor function from the Reynolds stress eld based on the hypothesis that its form is largely determined by the constraints imposed by inhomogeneity and continuity. Estimates for the plane wake compare favorably with measurements, and, interestingly, proper orthogonal modes and characteristic eddy structures inferred from the estimates are similar to those obtained from measurements. This implies that these measures of the correlation function are largely determined by fairly basic physical information, suggesting some simpli cation of the turbulence-modeling problem for applications such as aeroacoustics.

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Wave Number Frequency Spectra of a Lifting Wake for Broadband Noise Prediction

Cited by 9 publications

References 8 publications

Turbulence Correlation Length-Scale Relationships for the Prediction of Aeroacoustic Response

Turbulence Correlation Length-Scale Relationships for the Prediction of Aeroacoustic Response

Concept, design and characterization of a small aeroacoustic wind tunnel facility with application to airfoil measurements

Two-Point Descriptions of Wake Turbulence with Application to Noise Prediction

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