| The main target of the paper is to apply this high-level numerical simulation technique, i.e., large eddy simulation (LES) method, to the research of engineering problems. Therefore, the paper establishes the parallel computing platform and meets the demand of computing resources for large eddy simulation. It also studies the integration of CAD/CAM, grid generation system and CFD system, and brings the model computed in the paper into this system. On the bases of systematical and thorough numerical simulation researches in circular cylinder and the compares between instantaneous PIV metrical results and numerical results of circular cylinder, the paper obtained some problems and several conclusions which should be noticed in LES for making correct computatioa Finally, by using these experiences and conclusions above and by putting them into an actual problem in engineering-optimized numerical simulation of static mixer, this paper achieved the turbulent high-level numerical simulation technique, i.e., systematical attempt in engineering application by LES method.The main tasks of the paper are as follows:Firstly, it did a full and systematic research on CAD/CAM, grid generation and CFD software, which are now main streams. Discussed the importance operation and the value of wild application industry of system integration, provided concrete methods for the integration and built two kinds of grids by the methods that are used in the research.Secondly, it put forward a thought of parallel computing by computers so as to resolve the computing resources for this large eddy simulation. For that purpose, it did a research on the classification of parallel computing, LINUX operating system, the establishment of local net and the achievement of net environments MPI. It built a parallel computing platform, which had four knots and tested the fundamental functions of this platform. It is found that when the number of the grids is over 512000, the efficiency of two parallel computers is more than 67.9%, and over 52.8% by four computers. And the efficiency will improve as the grid number increases. The result of the test dictated that the efficiency of these small-scattered parallel computers is satisfied.Based on all of the work above, this paper studied circular cylinder by the method of large eddy simulation. It is found that the couple of Foppl vortex is unstable from the beginning when it engendered. The changing frequency is very slow at first, almost 2.5%~3% of the frequency when it is stabled. The amplitude is also so limited at the beginning the maximum is only about 0.035%~0.05% of the amplitude when it develops fully. By using the method of construct boundary condition at the entrance, it did a research on the formation principle of Karman vortex and believed that there was no direct relationship between the formation and the object itself. The existence of the object just provided a basic current in the space to generate a absolutely unstable district and so the explanation of absolutely unstable model near wake flow is more suitable. By using three different ways to discuss feasibility of two equations of k - s pattern to compute circular cylinder, it hold that two equations of k pattern is unsuitable to compute the unstable problems about circular cylinder. When it was studied under different turbulent intension about circular cylinder, it is found that the obstruction curve change greatly as the altering of the intension. But not so much after the result is averaged. The large eddy simulation of three dimension circular cylinder shows that: the calculation result fit perfectly to the experiment. By comparing convection term difference scheme of CD and QUICK, it is found that there is no obvious difference between these two schemes, and CD scheme is a little better. By comparing the results between two dimension simulation and three dimension, it deemed that the results are very close to each other when under lower Re number, but varied quite under high Re number.In company with the test syst...
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