Study of 3D Wall Roughness Acoustic Receptivity on an Airfoil

Würz, W.; Herr, S.; Wörner, A.; Rist, Ulrich; Wagner, Siegfried; Kachanov, Y. S.

doi:10.1007/978-3-662-03997-7_11

Cited by 3 publications

(3 citation statements)

References 3 publications

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“…One can see that the vortex-roughness receptivity amplitudes increase with frequency in a linear way. Similar frequency dependence was observed in several previous investigations of other localized receptivity mechanisms; for instance for receptivity to surface vibrations Bake et al 2002b) and acoustical receptivity in the presence of surface vibrations (Würz et al 2003(Würz et al , 2005. The frequency dependence of the ratio of the receptivity amplitudes G vr2 /G vr1 (shown in figure 26a) increases with frequency in a linear way, as well.…”

Section: Vortex-roughness Receptivity Coefficients and Their Propertiessupporting

confidence: 73%

“…Such terminology is widespread and used in a great number of previous investigations (see e.g. Gaponenko et al 2002;Würz et al 2003Würz et al , 2005 despite, strictly speaking, all receptivity mechanisms being nonlinear by their physical essence because they provide redistribution of the disturbance energy between different modes of the frequency-wavenumber spectrum and correspond to interaction between one or more types of external disturbances with the base flow and with each other.…”

Section: Regimes Studies and Measurement Proceduresmentioning

confidence: 98%

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Receptivity coefficients at excitation of cross-flow waves by free-stream vortices in the presence of surface roughness

et al. 2013

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The present experimental study is devoted to examination of the vortex receptivity mechanism associated with excitation of unsteady cross-flow (CF) waves due to scattering of unsteady free-stream vortices on localized steady surface non-uniformities (roughness). The measurements are carried out in a low-turbulence wind tunnel by means of a hot-wire anemometer in a boundary layer developing over a 25 • swept-wing model. The harmonic-in-time free-stream vortices were excited by a thin vibrating wire located upstream of the experimental-model leading edge and represented a kind of small-amplitude von Kármán vortex street with spanwise orientation of the generated instantaneous vorticity vectors. The controlled roughness elements (the so-called 'phased roughness') were placed on the model surface. This roughness had a special shape, which provided excitation of CF-waves having basically some predetermined (required) spanwise wavenumbers. The linearity of the stability and receptivity mechanisms under study was checked accurately by means of variation of both the free-stream-vortex amplitude and the surface roughness height. These experiments were directed to obtaining the amplitudes and phases of the vortexroughness receptivity coefficients for a number of vortex disturbance frequencies. The vortex street position with respect to the model surface (the vortex offset parameter) was also varied. The receptivity characteristics obtained experimentally in Fourier space are independent of the particular roughness shape, and can be used for validation of receptivity theories.

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Section: Vortex-roughness Receptivity Coefficients and Their Propertiessupporting

confidence: 73%

Section: Regimes Studies and Measurement Proceduresmentioning

confidence: 98%

Receptivity coefficients at excitation of cross-flow waves by free-stream vortices in the presence of surface roughness

et al. 2013

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“…Cullen & Horton (1999) studied the acoustic receptivity for a stationary localized three-dimensional roughness in a two-dimensional boundary layer, but no quantitative receptivity coefficients were evaluated. For the first time, these coefficients were obtained experimentally by Würz et al (1998) for a single acoustic frequency and compared with calculations in Würz et al (1999). The subsequent development of these studies is discussed in the present paper.…”

Section: Introductionmentioning

confidence: 87%

Three-dimensional acoustic-roughness receptivity of a boundary layer on an airfoil: experiment and direct numerical simulations

et al. 2003

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The paper is devoted to an experimental and numerical investigation of the problem of excitation of three-dimensional Tollmien–Schlichting (TS) waves in a boundary layer on an airfoil owing to scattering of an acoustic wave on localized microscopic surface non-uniformities. The experiments were performed at controlled disturbance conditions on a symmetric airfoil section at zero angle of attack. In each set of measurements, the acoustic wave had a fixed frequency fac, in the range of unstable TS-waves. The three-dimensional surface non-uniformity was positioned close to the neutral stability point at branch I for the two-dimensional perturbations. To avoid experimental difficulties in the distinction of the hot-wire signals measured at the same (acoustic) frequency but having a different physical nature, the surface roughness was simulated by a quasi-stationary surface non-uniformity (a vibrator) oscillating with a low frequency fv. This led to the generation of TS-wavetrains at combination frequencies f1,2=fac ∓ fv. The spatial behaviour of these wavetrains has been studied in detail for three different values of the acoustic frequency. The disturbances were decomposed into normal oblique TS-modes. The initial amplitudes and phases of these modes (i.e. at the position of the vibrator) were determined by means of an upstream extrapolation of the experimental data. The shape of the vibrator oscillations was measured by means of a laser triangulation device and mapped onto the Fourier space.

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Three-dimensional receptivity of boundary layers

Kachanov

2000

European Journal of Mechanics - B/Fluids

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Study of 3D Wall Roughness Acoustic Receptivity on an Airfoil

Cited by 3 publications

References 3 publications

Receptivity coefficients at excitation of cross-flow waves by free-stream vortices in the presence of surface roughness

Receptivity coefficients at excitation of cross-flow waves by free-stream vortices in the presence of surface roughness

Three-dimensional acoustic-roughness receptivity of a boundary layer on an airfoil: experiment and direct numerical simulations

Three-dimensional receptivity of boundary layers

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