An experimental study of oblique transition in a Blasius boundary layer flow

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摘要：

Transition initiated by a pair of oblique waves was investigated experimentally in a Blasius boundary layer flow by using hot-wire measurements and flow visualisation. The oblique waves were generated by periodic blowing and suction through an array of pipes connecting to the flow through a transverse slit in the flat plate model. The structure of the flow field is described and the amplitude of individual frequency-spanwise wave number modes was determined from Fourier transforms of the disturbance velocity. In contrast to results from investigations of oblique transition at subcritical flow conditions, the transition process at the present conditions suggests the combined effect of non-modal growth of streaks and a second stage with exponential growth of oblique waves to initiate the final breakdown stage.

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关键词：

Experimental/ boundary layers flow visualisation Fourier transforms waves/ oblique transition Blasius boundary layer flow hot-wire measurements oblique waves flow visualisation periodic blowing and suction transverse slit flat plate model flow field frequency-spanwise wave number modes Fourier transforms disturbance velocity subcritical flow conditions nonmodal growth/ A4715C Laminar boundary layers A4725F Boundary layer and shear turbulence A4735 Waves in fluid dynamics