Generation of disturbances in the boundary layer of a flat plate by periodic low-frequency motion of the surface section

Abstract

The development of localized disturbances, generated by periodic impulse lifting of three-dimensional surface in the flat plate boundary layer at Reδ1 > 400 is experimentally investigated. It is shown that a large amplitude surface lifting leads simultaneously to the formation of two types of perturbations in the boundary layer: longitudinal localized structures and two wave packets. Spatial development of oscillations at the central frequency of the wave packets is consistent with the linear theory of hydrodynamic stability.