Investigation Of Large Eddy Simulation And Coherent Structure For The Flow Field Of Turbine Vane

Turbulence is a kind of very complex flow. Up until now, people on the understanding of themechanism of turbulence is not perfect, still in the exploration. Turbulence in the engineeringtechnology question also often involves the important problem. How accurate numerical simulation ofturbulence complex flow field, the turbulent research become into one of the most important goals. Inrecent years the development of Large Eddy Simulation method is special attention by people. In thisarticle, Large Eddy Simulation was used to carry out the accurate numerical simulation of turbulentflow field and the Basic theory research of Coherent structure，which turbulent flow field has closerelations with air gas turbine，and the improvement of the performance of the engine is closely relatedto its research work. It is has important theoretical significance and application value.Compressible flow Large Eddy Simulation algorithm with high precision and high efficiencywas developed in the paper, its content mainly includes：1) The governing Equations of the non-dimensional Large Eddy Simulation and dynamicsub-grid scale model specific form of this article is derived in the general curvilinear coordinatesystem. Then the preconditioned algorithm is used in the code to expand the scope of the program’scalculation, so that it can calculation of transonic flows and low-Mach number flows, such as the flowfield of turbine vane with the film cooling.2) The finite volume methods take advantage of the integral form of the governing equation toachieve a algebraic discrete approximation for numerical calculations. In order to ensure generatednumber the discrete error did not exceed the influence of the sub-grid scale model, the numerical fluxwas calculated by six order precision WENOSYM scheme and Compact scheme. The WENOSYMscheme was adopted on calculation of the Convection flux. The Compact scheme was adopted oncalculation of the viscous flux and the specific coefficient was deduced.In this paper, the implicit Newton iteration scheme was used for temporal discretization. Thenthe analytical S-W Jacobians formula and simplify Roe Jacobians formula of implicit Jacobiansmatrix was deduced. The engineering practicability of Roe Jacobians matrix was confirmed. Thiswork makes a good evolution for the implicit method.3) In the process of computation, a given imported disturbance in the boundary layer is using asynthetic vortex approach. The computation result shows that the flow in calculation domaindeveloped turbulence after a short development section. The application of the approach is theengineering application of positive preparation. The turbulent boundary layers fields related to Coherent structure and the flow characteristicswere further research in the paper. Its content mainly includes:1）Coherent structure in the inner layer of the flat channel turbulent boundary layer is analyzed.Solution of the flow field statistical average was compared with the empirical formula and DNS result,and the characteristic parameters of large eddy coherent structures was compared with Cantwell’sparameters. The results of comparison were very well. The two kinds of hairpin vortex packetstructures of the calculated results were compared with experimental results to confirm its structure.Studying the temporal evolution process of coherent vortex structures, the hairpin vortices withunilateral vortex leg formation process was discussed. This conclusion of the hairpin vortices in theflat-wall turbulence is still not seen in the literature.2）Hairpin vortex structure of the Jet into Cross-flow and the method of Pulsation optimizing filmcooling efficiency was discussed. On the research of the flat basis, the flow field of the Jet inCross-flow that was applied in the gas turbine film cooling is studied. Through the analysis of thestructure and development of the hairpin vortices in flow field, the flow’s characteristics of the Jet inCross-flow were learned. Then combined with the literatures, the idea that the hairpin vortices in themain body of jet are control by the pulsed jet is proposed. Through the analysis of the pulsed jet flowfield simulation results, the initial conclusions are that the pulsation controls the intermittent existenceof the hairpin vortices’ group and the interval between the hairpin vortices’ groups corresponding tothe frequency of pulsation.3）Coherent structure form In the transition process on flow filed of MT1turbine vane is to show.Flow fields of the MT1turbine guide vane with film cooling and without film cooling were simulated.Without film cooling, coherent structures of shock-induced separated flow transition were showed onthe suction side of the blade. With film cooling, the forms of coherent structures that was produced byfilm cooling jet in different locations on blade surface were researched, and the influence thatcurvature of wall surface has an effect on jet’s structures were discussed, and the vortex stretching byinfluence of reverse transition were shown.Obviously, in this paper the Large Eddy Simulation algorithm and to the research of theturbulence’s Coherent structure are closely related. The Large eddy simulation Algorithm providestechnical support for the research of Coherent structure, and the research provides researchfoundation and the theoretical basis for the practical application of the LES in flow field of turbinevane, that the research is related with flow field of flat，the Jet into Cross-flow，and the turbine vane.