Wind Load Characteristics Of Moving Tornado On Low Rise Buildings

Tornado is a disastrous natural weather phenomenon,which has small horizontal scale,fast moving speed and short duration,and it has a wide range of active areas all over the world.Human beings have gained a deeper understanding of tornadoe with means of theoretical methods,radar research,lab simulation and numerical computation.Because of the complex structure of the tornado flow field,it is difficult for researchers to fully understand its mechanism and mode of action in the short term.In this paper,a numerical simulation method based on computational fluid dynamics(CFD)is used to study the generation method,evolution law of the moving tornado wind field and its influence on the wind load of the building.The specific research contents of this paper are as follows:Using the measured wind velocity profile of Spencer tornado as an entrance boundary condition,the influence of factors such as grid type and quantity,turbulence model,surface roughness and roughness height on tornado wind field structure are studied,so a high precision CFD numerical model of tornado wind field isestablished,which lays the foundation for studying the mechanism of wind field evolution and the tornado load on buildings.On the basis of the numerical model of tornado wind field established above,the variation of the maximum tangential velocity and core radius of the tornado wind field is studied by changing the wind velocity profile and the incidence angle profile of the tornado wind field,and the evolution mechanism of the tornado wind field with different scales and different intensity is obtained.In the EF3 level static tornado wind field,research the distribution of the surface wind pressure coefficient,the vortex core area map of the wind field,the velocity vector and the trace map of the buildings in different positions,with different forms of opening and opening rates,with different roof slopes under different angles.It reveals the structure load characteristics and failure mechanism in tornado wind field.By groundmoving equivalent simulated moving tornado,it can obtain the characteristics of the moving wind field.On this basis,use dynamic grid technique to realize the wind load simulationof equivalent moving tornado on buildings,and compare thebuilding surface wind pressure coefficient between different move speed tornado and static tornado,it can reveal the influence of moving tornado on buildings better.