Borodulin V.   Ivanov A.   Kachanov Y.   Mischenko D.   Örlü R.   Hanifi A.   Hein S.  

Initiation of three-dimensional Tollmien-Schlichting waves in swept-wing boundary layer by surface vibrations

Reporter: Borodulin V.

The paper is devoted to quantitative experimental study of a mechanism of excitation of three-dimensional Tollmien-Schlichting (TS) waves in a boundary layer of a 35-degree swept wing by unsteady surface nonuniformities. The experiments are performed in the Royal Institute of Technology in Stockholm (Sweden) in the framework of studies ‘B’ of Working Package 1 of project ‘RECEPT’ of the Seventh European Framework Program. The measurements are carried out on a model of a real swept wing of an infinite span at conditions of controlled surface perturbations. Calculations and measurements have shown that at the selected angle of attach of +1.5°, the TS instability dominates in the boundary layer, while the cross-flow instability is absent due to very low cross-flow intensity at conditions of very weak streamwise pressure gradient. The base- flow and the disturbance parameters (such as frequencies and spanwise wavenumbers) were selected based on calculations, performed for the particular experimental conditions, as well as on preliminary experimental studies of the 3D TS instability. The calculations have shown a very good agreement of stability characteristics with the measurements obtained in a broad range of frequencies, spanwise wavenumbers, and TS-wave propagation angles. As a result of deep processing of the experimental data, estimates of values of coefficients of linear flow receptivity to streamwise localized surface vibrations are obtained for excitation of the 3D TS waves. The results are obtained for various values of the disturbance frequency and spanwise wavenumber.

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