A Numerical Study on the Wind Environment of the FAST

The main structure of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) will be constructed in a complex Karst landform.The FAST primary reflector will have to function with the presence of wind load.A wind-resistant design is necessary for the FAST.Currently,the field-test,wind-tunnel test,and numerical-simulation approaches are the three main methods to acquire the wind-pressure coefficients.Normally,a field test is not economic either in labor cost or financial expense.A wind-tunnel test is also expensive.For this study,numerical simulations are chosen for a preliminary study.Any field test will be performed in future if necessary.We construct certain geometric models,mesh models,and CFD (Computational Fluid Dynamics) analysis models for the FAST reflector and its surrouding terrains.The CFD models are built for the FAST reflector and the surrounding landform within 40km×10km×5.5km.A reference altitude of 810m is used for the profile of wind velocity at the inlet.We use the model to investigate the pressure coefficients of the reflector for different wind directions.For a panel of 35.4% perforation rate, we perform numerical analyses to acquire the relation between wind speed and pressure drop across the panel. The calculated aerodynamic coefficients are consistent with previous screen test results within 3%.Combining with porous jump boundary conditions,we use the methods to simulate the aerodynamic performance of the FAST reflector.We obtain the distributions of the wind pressure coefficients for multiple wind directions.The results show that the wind direction is a major factor and at the 5.5 o'clock direction wind can have the most sever effects.Our simulation results show that the choice of windbreak height is of more importance than the choice of windbreak position.The results can be used as references for the wind-resistant design of the FAST, the subsequent construction procedure,and the high-precision measurement and control of the FAST reflector.