**AUTHORS:**Yuli D Chashechkin, Yaroslav Zagumennyi

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**ABSTRACT:**
Based on the fundamental system of equations a numerical approach is constructed for calculating in a single formulation various flows of strongly and weakly stratified fluids, which are typical for laboratory and environmental conditions, and potentially and actually homogeneous fluids, which are, respectively, physically valid and approximate mathematical models for “pure water” medium. The numerical method is developed in the framework of the open-source programming tools, OpenFOAM package, using high-order discretization schemes for all the derivatives in the governing equations and high spatial-temporal grid resolution of the computation domain. Unsteady flow patterns for the basic physical parameters, i.e. velocity, density, and pressure, and their derivatives, are studied around a thick and a thin rectangular horizontal plate for the fluid types under consideration. Comparison of the calculated velocity profiles and drag distribution on the surface of a horizontal plate with the Blasius solution for semi-infinite plane showed a strong influence of plate’s thickness on the boundary layer flow structure and dynamics.

**KEYWORDS:**
Stratified medium, homogeneous fluid, horizontal plate, internal waves, vortices, numerical simulation, OpenFOAM

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