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Generation of localized disturbances by surface vibrations behind the ledge in the laminar flow

“…Taking into account [4], the impulse action of the membrane on the boundary layer leads to the formation in it of perturbations of two types: a streaky structure localized in the direction transverse to the flow and wave packets of oscillations near its forward and rear fronts. The motion of the membrane located within the separation region causes a similar result.…”

“…The origin and evolution of packets were studied in previous experimental works with the participation of the authors of this article in modeling streaky structures of the boundary layer in various ways. Among them, the generation of structures by the blowing-in of air through the slots in the streamlined surface, its localized vibrations, and by perturbations of the vorticity of the incoming flow in gradient and gradient flows [4][5][6][7][8][9][10][11][12].…”

Experimental investigation of localized disturbances in the straight wing boundary layer, generated by finite surface vibrations

“…The disturbance length (200 ms) is equal to the length of pulse, which moves the membrane upward. This structure is corresponding to the longitudinal localized streaky structures, or so-called "puff" structures, which are in more detail investigated at [3][4][5][6][7][8][9][10][11]. Going downstream, the flow pulsations of this structure (u min and u max ) become weaker.…”

“…With the presence of adverse pressure gradient flow region a high-frequency wave packets appears and grow rapidly. This paper is a continuation of the research [7]. Here, the behavior of longitudinal localized structures and wave packets in regions of favorable and adverse pressure gradient and flow separation area is experimentally studied in detail.…”

“…In addition to the widely used suction-injection technique [4,5], another method is also used where the boundary layer disturbances are generated by vibrations of a local surface area. Experimental investigation of the origin and development of disturbances, generated by vibration of three-dimensional surface in the Blasius boundary layer is shown in [6] and for the straight wing boundary layer in [7]. It was found, that in the boundary layer the elongated localized disturbances with were generated.…”