Numerical Simulation Study Of Wind Load On Low-rise Buildings

In this thesis numerical simulations are conducted to calculate the pressure on the surface of the low-rise building by means of computational fluid dynamics. The main concern of this thesis is to find the key factors of grid generation. The grid generation determines the style of domain's division and the govern equation's discreteness. To arrive at the highly accurate result of the fluid pattern around the low-rise building, we need to know how to obtain the mesh which is fine enough. There are two ways to fine the mesh: minimize the first cell's height and reduce the stretch ration. So the accuracy requirement limits the height of the first cell. Meanwhile, it is important to simulate the flow near the wall with high accuracy to analysis the whole domain. Wall function is always utilized to solve this problem. But wall function also brings limitation to the first cell's height.Firstly, the author tried to minimize the artificial factor during the modeling process. So the structure mesh is used during the simulation of the TTU model. By comparing the simulation result and the test data, the author finds three key factors during the grid generation.Secondly, a series of wind tunnel tests which is conducted in the Tokyo Polytech University's wind tunnel are simulated to analysis the effect of the geometry on the cell' height. The height and pitch of the numerical models are varied to simulate different wind tunnel tests. The cell's height and stretch ratio are also varied to obtain the mesh-independent-result and to satisfy the requirement of the wall function.Thirdly, with the purpose of summarizing the ordinary rule of grid generation, the author deduce the formula to estimate the first cell's height by means of applying the plate's boundary layer theory to the low rise building within the Reynolds number's scope of 2.3×10~6～2.58×10~7. Validation of this formula is conducted with the numerical result. A hybrid mesh system is introduced to model the boundary layer.The last part is the conclusion of this thesis and suggestion to further research.