Research Of Simulation Method About Homogeneous Turbulence Field Based On Oscillating-grid In Wind Tunnel

With the increase of the architectural layers and the innovation of the building size,the wind tunnel test, as one of the main means of researching building`s wind response,is more and more getting the wide attention of the society, and the realization of simulating the atmospheric boundary layer in wind tunnel has been more studied by scholars. Currently, the combination system of spires and roughness elements is a major means of simulating atmospheric boundary layer in wind tunnel, which can simulate the wind profile curves well under various geomorphic types, but for the turbulent intensity curves, especially on the flow field, it always can`t get a satisfactory result. It will cause greater error if the turbulence intensity is too small in wind tunnel experiment. For improving the turbulence intensity and reduce the wind tunnel experiment error, this article will realize the simulation of the atmospheric boundary layer in wind tunnel by the combination system of the vibrating grid, spires and roughness elements. The main contents include:Analyze the shape parameters, vibration parameters and the location parameters of the vibrating grid, and study the corresponding relations between the different parameters and wind velocity and turbulence intensity, and get a method based on the vibrating grid for the simulation of atmospheric boundary layer in wind tunnel. Draw conclusions as following: in order to the turbulent intensity in the flow field has good uniformity, the grille blocking rate should be between 35% and 45%., and increasing the width of grating can enhance the turbulence intensity. The number of bars has little effect to turbulence intensity, but it can effectively improve the uniformity of flow field.Increasing the vibration frequency and amplitude also can enhance the turbulence intensity, but it also causes that the fluctuations of turbulent intensity is increasing, so the vibration parameters of grating should not be too big. The turbulence intensity is affected greatly by the location parameters of vibrating grid. In the wake flow field of grid, the distance to get uniform stability for the field is the smaller values between the height and the width of the wind tunnel. In uniform flow field, the scope of turbulence intensity modulated by grid position distance also reaches 7%- 21%. The inflow windhas little effect on the turbulence intensity, but it changes the wind speed in the wind tunnel.Build the portfolio model of the vibrating grid, spires and roughness elements, and study the wake characteristics of the portfolio model, and get the method based on the portfolio model for the simulation of atmospheric boundary layer in wind tunnel.Studies have shown that increasing the bottom width and the number of the wedges can effectively reduce the wind speed and improve the turbulence intensity in the lower flow filed, and it can greatly change curve contour, which has great effect to fit of the velocity curve. The law of increasing the height of wedge is same as increasing the bottom width, but the change of wind speed and turbulence intensity is small, so the method is suitable for fine-tuning. At the same time, it has little influence for the upper flow field to increase the number of the wedge, but it can significantly increase the turbulence intensity and reduce wind speed in the lower part of flow field. So it is helpful to improve the simulation for the lower part of the wind field. Reducing the distance between roughness elements and the test center is effective only near-earth for the turbulence intensity, and no obvious effect on other properties.Based on the above research, full-scale model of HITSZ wind tunnel laboratory is went up. In this paper, the vibrating grid, spires and roughness elements are introduced to study the numerical simulation of atmospheric boundary layer in wind tunnel. In the debugging process, this paper uses A, B, C, D four geomorphic types to be reference.Firstly, adjust the number and the bottom width of wedge to fit the upper curve of the wind speed. Secondly, according to the characteristic of the curve to adjust the upper curve of the turbulence intensity. Finally, adjust the lower flow field by fit the roughness elements and do error analysis. It is concluded to the design parameters of devise for the simulation of the atmospheric boundary layer in wind tunnel and verify the validity of the above simulation method.