The Research And Application Of Multi-Grid Method In Numerical Simulation For Wind Turbines Flow Field

The wind turbine medium is actualy low speed and low temperature air, and wind turbine flow field is a compressible, sticky and nonstationary flow field, the mathematical model of which is nonstationary, nonlinear partial differential equations of determining solution. However, Aiming at solving this kind of partial differential equations, the usual numerical methods not only need huge computional cost, but also involve many aspects of the numerical techniques. Solving algebraic equations arising from numerical methods for the partial differential equations will occupy most of the time required for the calculation. As a kind of fast calculation method, multi-grid method can save a lot of calculating time for solving the algebraic equations. The basic principle is that the different error components can be eliminated in the different spacing grid:eliminating the error components of high frequency in fine mesh, and the error components of low frequency in coarse grid. At present, the multi-grid method has been widely used in various fields of the numerical calculation problem, and has a broad prospect.In order to overcome the defect, the traditional iterative method of which has huge computional cost and slow convergence rate, for solving high-dimensional problems, the paper will apply the multi-grid method to the numerical simulation of the wind turbine flow field problems as accelerated technique. Firstly, the paper introduces the development, the basic principle, the basic step and the applied principle of multi-grid method, and analyses the convergence of two-grid method that is key part of the multi-grid method by the example of poisson equation. Secondly, for the mathematical model of the wind turbine flow field problem being nonstationary and nonlinear partial differential equations, it constructs the restriction operator, interpolation operator and smooth iteration scheme of the multi-grid method, and gives the numerical algorithm of the finite difference method, the Newton iteration combining with the multi-grid method. Finally, it gives the corresponding computer programs by the Visual Fortran Language, and does the simulative computing for the actual numerical example. The numerical results shows that the method given in this paper can reduce the computation time 50% more than the traditional iterative method (the finite difference method + Newton iteration method + successive overrelaxation iteration method). The numerical simulation of wind turbine flow field problem proves the feasibility and effectiveness of this method.