Receptivity coefficients at excitation of cross-flow waves due to scattering of free-stream vortices on surface vibrations

Abstract

This paper is devoted to an experimental investigation of receptivity of a laminar swept-wing boundary layer due to scattering of free-stream vortices on localized (in the streamwise direction) surface vibrations. The experiments were conducted under completely controlled disturbance conditions by means of a hot-wire anemometer on a model of a swept wing with a sweep angle of 25 • . Both the free-stream vortices and the surface vibrations were generated by disturbance sources; their frequency-wavenumber spectra were measured thoroughly. The free-stream vorticity vectors were directed perpendicular to the incident-flow velocity vector and parallel to the swept-wing-model surface. The linearity of the receptivity mechanism under investigation (in a sense that the corresponding receptivity coefficients are independent of the disturbances amplitudes) has been checked carefully. The main goal of this experiment was to estimate the vibration-vortex receptivity coefficients as functions of the disturbance frequency, spanwise wavenumber and vortex offset parameter. This goal has been attained. Being defined in Fourier space, the obtained receptivity coefficients are independent of the specific surface vibration shape and can be used for verification of various receptivity theories.

Receptivity coefficients of vortex-vibrational type at excitation of 3D Tollmien-Schlichting waves in a boundary layer on a swept wing

“…Estimates of the corresponding localized receptivity coefficients were obtained for the "vortex-vibrational" [5,6] and "vortex-roughness" [7] receptivity mechanisms. Similar results were obtained later for a 3D, swept-wing boundary layer at excitation of cross-flow (CF) instability modes by both vortex-roughness [8] and vortex-vibrational [9] localized receptivity mechanisms. The excitation of nonstationary Görtler instability modes due to scattering of freestream vortices on localized surface nonuniformities was investigated recently in experiments [10].…”

“…The excitation of TS-waves by a vortex-vibrational receptivity mechanism can be characterized quantitatively by the so-called receptivity coefficients (see [8,9] for instance):…”

Excitation of 3D TS-waves in a swept-wing boundary layer by surface vibrations and freestream vortices

“…Most of theoretical and experimental works on stability and receptivity problems in a swept wing boundary layers deal with cross-flow waves and vortices, see e.g. reviews in [1][2][3]. Meanwhile in some cases, say on a suction side of a long laminar run wing installed at moderate positive angle of attack, TS waves may win the competition with crossflow waves and predominate in transition to turbulence.…”

Generation of unsteady CF-instability modes by vibrational and vibration-vortex localized receptivity mechanisms

“…A detailed review of the state of the art in the field of investigations of localized receptivity mechanisms responsible for excitation of steady and unsteady CF-instability modes in swept-wing boundary layers can be found in refs. [1][2][3]. In this section, we mention only the most significant aspects of the present study and its motivation.…”