18.06.2020

DEFENCE Redchyts

Redchyts D.O. "UNSTEADY COUPLED PROBLEMS OF THE DYNAMICS OF A LIQUID, GAS, AND LOW-TEMPERATURE PLASMA" (Doct. Phys.-Math. Sci.)

HYDRODYNAMICS AND ACOUSTICS

2018 ◊ Volume 1 (91) ◊ Issue 3 p. 316-333

N. F. Dimitrieva*

* Institute of Hydromechanics of NAS of Ukraine, Kyiv, Ukraine
**National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute"

Flows around a 2D horizontal wedge in a steadily stratified liquid

Gidrodin. akust. 2018, 1(3):316-333

https://doi.org/10.15407/jha2018.03.316

TEXT LANGUAGE: Russian

ABSTRACT

The paper deals with studying of the flows of continuously stratified fluid characterized by a wide range of values of internal scales that are absent in a homogeneous fluid. The problem is solved by numerical methods in a 2D unsteady formulation for a fluid at rest and uniform motion. For the mathematical description of the problem, a system of differential equations of mechanics of inhomogeneous multicomponent fluids was chosen in the Boussinesq approximation with considering the small density variations only in terms describing the gravity force. The problem is solved by the method of finite volumes in a free software package OpenFOAM. The particular attention was paid to creation of a high-quality high-resolution computational grid taking into account the multi-scale diffusion-induced flows. The use of standard and advanced utilities of the OpenFOAM package to implement the complex boundary conditions and develop new numerical models is discussed. The fields of diffusion-induced flows on a fixed wedge being in qualitative agreement with experimental data are used for initial conditions in the problem of external flow of a stratified medium around the wedge. The influence of edge effects and curvature of edge lateral surface on the flow structure is shown. The results of calculation reveal the extended region of pressure deficit at the acute top forming the integral force that is the reason for self-motion of free wedge in apex direction along the neutral buoyancy horizon in stably stratified medium. In stratified fluid, the evolution of flow pattern of the wedge starting the uniform motion from the rest at the velocity of 10-4 m/s is demonstrated. In all regimes, the flow is characterized by complex internal structure with the initially expressed dissipative-gravity waves and further emerging group of attached waves forming in antiphase at wedge's edges. With the increase of external flow velocity vortices dominating in the wake become the main component of the flow.

KEY WORDS

numerical simulation, open computing packages, stratification, fluid flow, diffusion, self-motion

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