Numerical Wind Tunnel Technique And Application Study Based On Large Eddy Simulation Method

Numerical wind tunnel is an aerodynamic numerical simulation system that hasthe key attributes of the real wind tunnel. Compared with the field measurements andphysical tunnel test, numerical simulation has the following advantage: the structureand the scale have no effect on the object of study; researcher can study the impact ofdifferent parameters on the flow field in detail; and can obtain the information of flowfield that field measurements and tunnel test can not provide; numerical simulationhas the short cycle, high efficiency, cost saving advantages. Over the past ten years,many scholars at home and abroad studied many problems on structural windengineering by numerical wind tunnel method, and had achieved very nice results.However, due to the complexity of the problem, there are still many problems intechnology and application using the numerical wind tunnel method to solve thetheory research of design of wind-resistant of engineering structure. In this paper, themain contents are as follows:Firstly, deduced the Navier-Stokes equations of LES based on the LES method.Secondly, discreted three-dimensional turbulent flow control equations used centraldifference scheme based on the finite volume method, obtained the three-dimensionaldiscretization equations of control equations; Finally, three-dimensional discreteequation algorithm SIMPLE algorithm implementation steps and boundaryconditions,and analyzed of the discrete equations iterative methods.On this basis,developed a multi-grid generation program and solution program of three-dimensionalnumerical wind tunnel.Calculation procedure of the paper developed a three-dimensional numericalwind tunnel calculated and analyzed jet flow field and SFG7-4-type axial fan externalairflow velocity field.The results show that the jet flow field has a certainself-preservation.The results of the program calculation found, in accordance with the parameters set, the length of the core area of jet flow is4cm.0~0.9m program tocalculate the results and software simulation results is very close, there is a certainerror between0.9m and1.0m; wind speed gradually decreases with increasing lengthof exports monitor dot pitch. The air-velocity field of SFG7-4axial flow fan wassymmetric distribution, the peak value of velocity decreased gradually along the flowdirection, when the distance to the outlet of the blower was3m, the peak value ofvelocity of the section in the center line of axis; the change of air-velocity wasbecoming smooth along the flow direction, when the distance to the outlet of theblower was5m, in the range of0~0.5m away from the center line of axis, speed ismore evenly distributed. In this paper, compared the calculation results of the program,the simulation results of FLUENT software and measured results, the results showthat, program calculation and software simulation can accurately predict the changetrend of air-velocity of fan, but the program calculation values were more approach tothe measurement values.