Borodulin V.   Ivanov A.   Kachanov Y.   Mischenko D.   Орлю Р.   Ханифи А.   Хайн Ш.  

Excitation of unsteady cross-flow instability modes at scattering of free-stream vortices on surface vibrations

Reporter: Ivanov A.

The results of quantitative experimental study of a mechanism of excitation of unsteady (in general)

cross-flow instability modes in a boundary layer of a 35-degree swept wing due to scattering of unsteady free-

stream vortices on streamwise localized surface vibrations are presented in this paper. The experiments are

performed in the Royal Institute of Technology in Stockholm (Sweden) in the framework of studies ‘A’ 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 −5°, cross-flow instability

dominates in the boundary layer. The base- flow parameters, as well as the parameters of the frees-stream and

surface perturbations (such as frequencies and range of spanwise wavenumbers) were selected based on

calculations, performed for the particular experimental conditions, as well as on preliminary experimental

studies of the cross-flow instability. The calculations have shown very good agreement of stability

characteristics with the measurements obtained in a broad range of parameters. After deep processing of the

experimental data, estimates of values of coefficients of linear flow receptivity to freestream vortices (with

vorticity vectors parallel to the wing leading edge) at their scattering on streamwise localized surface vibrations

are obtained for the receptivity mechanism responsible for excitation of the cross-flow instability modes. The

coefficients are obtained for various relations of the vortex and surface frequencies in a great range of spanwise

wavenumbers of the excited cross-flow instability modes.

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