Zagumennyi I. Control problems of unsteady flow structure and integral characteristics of bodies

The thesis is devoted to the study of wave and vortex structure formation around bodies which can perform unsteady motions in homogeneous and stratified viscous fluids. The processes of interaction of different-scale flow structural elements in boundary layers and in the wake past bodies are studied, and the interrelations of flow structure with local and integral hydrodynamic characteristics of bodies are determined. A method for control of unsteady flow structure and integral characteristics of bodies is developed on the basis of new algorithms for direct numerical computations of flows around bodies performing unsteady motions. An algorithm for numerical solution of conjugate problems of fluid and solid mechanics is constructed using the finite volume method based on original program codes of own development of the OpenFOAM package with the open source. On the basis of the developed algorithm for numerical simulation of continuously stratified fluid flows, high-resolution calculations of stratified flows around various shaped obstacles are performed for the first time in a wide range of Reynolds and Froude numbers. A series of comparisons of the calculated stratified flow patterns with the relevant laboratory images obtained using schlieren instruments is conducted. The relationship of the boundary layer flow vortex structure with the hydrodynamic characteristics of the streamlined surface locally perturbed in the form of a traveling wave with a given amplitude, frequency and phase velocity is determined. The parameters of the traveling wave on the streamlined surface are revealed, which correspond to the effect of the boundary layer transition delay to turbulence. The conditions for the flow reattachment on a wing profile performing forced rotational-oscillating motions in the free stream are determined, as well as the conditions for intense propulsive force generation on the wing with a flexible tail element. The relation between the elastic characteristics, length and frequency of active excitation of a passive viscoelastic wing tail is determined, which corresponds to the antiphase mode of the forced and free oscillations of the deformable element and the greatest propulsive effect.