Mechanical & Aerospace Engineering

Biography

Biography: Vladimir Voskoboinick

Abstract

The boundary layer control is one of the actual sections of the modern hydromechanics dealing with investigations of vortical mechanisms in flows around bodies with an artificial roughness and improvement of aerodynamic characteristics of lifting surfaces. One of the well-known passive control techniques is vortex generation by roughness, which is used experimentally or numerically by many investigators. Dimples are some elements of a roughness. The symmetric and asymmetric large-scale vortical systems inside a spherical dimple are found out depending on the flow regime, and location and periodicity of their injection are shown. The evolution of coherent large-scale vortices subjected to a switch mechanism that is results in appearance of low-frequency modulating transversal oscillations of vortex motion inside the dimple. Discrete peaks are found out in spectral dependencies of pressure and velocity fluctuations. These local rises of the velocity and pressure fluctuation levels correspond to rotating frequency of the vortex systems inside the cavity, their injection frequency, wake mode frequency of oscillations of vortical movement inside the dimple, caused by a hydrodynamic resonance, and also self-sustained shear layer frequency of oscillations inside the dimple, which corresponded to a hydroacoustic resonance. The form and sizes of the quasi-stable large-scale vortex structures, the region of their origin and stages of development are submitted. Instantaneous and averaged characteristics of wall pressure fluctuations of vortical movement inside the cavity and in its near wake differ from each other, from nonlinear interaction of vortical structures with each other and streamlined surface.