Simulation of the Progress and Separation of the Boundary Layer Using the Method of Boundary Elements

Анотація

Detached flows of the bodies are the most widely spread phenomena in nature and in engineering. The main specific feature of them is that the flow becomes transient after the separation. This scientific paper is devoted to the direct numerical simulation of the eddy transient flow of 2D objects. The purpose of this investigation was to test the methods used for the solution of the problem of transient flow of different objects in order to define transient power loads and turbulent characteristics of the flow. To solve the problem of external flow of the bodies in the infinite space the eddy motion distribution is usually considered to be final. This allows us to concentrate computational resources on these areas, reaching there a high resolution of the flow structure at relatively low expenditures. A great advantage of vortex models is that these allow of the gridless realization. One more advantage of vortex gridless methods is the simplicity of meeting the boundary conditions for the infinity to solve the problems of external flow. A region occupied by the bodies is simulated as a liquid volume whose boundary has a tangential discontinuity of the velocity vector. The tangential velocity jump value is derived from the integral equation that provides the flow tangency condition on the body surface. The medium outside the streamline body and the vortex wake is considered to be ideal. A method of finite elements was used for the simulation of progress and separation of the boundary layer on the cylinder and the wing profile NACA 642-015A for the infinity flow. A change in the friction stress was calculated starting from the motion origination time. These data and the methods can be used for further improvement of hydrodynamic properties of different hydraulic machines including power and erosion indices and the optimization of hydrodynamic loads on blade systems.