Flow Simulation And The Research Of Structural Wind Effects

Spatial structures,which are becoming lighter,greater,and more shape complicated,brings new challenges to the structural wind engineering. Flexible features of spatial structure are increasingly obvious. The coupling effect between structure and wind is dramaticly remarkable. How to reveal the characteristics of the wind flow around the structure exactly and grasp the complex coupling mechanism is a very hot field which is to be urgently solved in today's theory and engineering community. Based on computational fluid dynamics and computational structural dynamics, wind-induced mechanical model and related algorithm on FSI(Fluid-Structure Interaction ) were studied.A fully explicit two-step temporal discretization characteristic based split (CBS) algorithm was developed based on multi-step Taylor expansion along the characteristic of the momentum equation and was applied to the simulations of unsteady flow past bluff bodies at low Renolds. Two-step CBS method has second order accuracy in time and retains all the properties of the original CBS method.The results were compared to the related research results in order to verify the present mehtod.The changes of fluid flow was studied,when there were objects interference.Generation and update methods of mesh grid of fluid domain and structure domain as well as the coordination and information transferring strategy of grids on the interface between flow field and structures were studied. A more accuracy,robust and efficient grid updating method called modified spring analogy(MSA) was put forward,with consideration of the impact of torsion spring.The modified spring stiffness was derived to improve the spring analogy method to adapt to the large distortion. NACA0012 airfoil flow which has complicate boundary was introduced to check the mesh quality which was updated by MSA under the large distortion. Furthermore, MSA was extended to structured grids updating by the mapping technique.On the other hand,the wind flow and pressure distribution with the interference effects were studied. The eddy viscosity of subgrid-scale stress in LES model was modified in order to improve the description of turbulence near the wall,and the present results was close to those of DNS. Based on the modified LES model, the simulation of wind flow and wind pressure distribution around the rigid and flexible objects were carried out. The improved technique was verified by series of comparison with other computational results based on different turbulence models. The results showed that the flow characteristics and wind pressure distribution between three objects case and single object were remarkably different.