Research On Downburst Wind Field And Its Wind Load To High-Rise Building Considering Moving Effect

Downburst is a strong downdraft air impinging on the ground during the thunderstorm,with an extremely high velocity generated close to the surface.Previous studies have focused on stationary downburst.However,the meteorological observations show that the actual downburst is affected by the wind field around the boundary layer,the storm center of which is moving.The moving effect of the storm will have an important impact on the wind field and the wind load of building structure.With the development of this subject,it is of great significance to investigate the characteristics of the actual downburst wind field and obtain the wind load characteristics of the structure under the wind field.In this paper,the wind field characteristics of moving downburst are studied by wind tunnel test and numerical simulation,and discussed the influence of storm movement on surface wind load on high-rise building.The paper's major works are given as follows:(1)The experimental investigation and simulation of the transient wind field characteristics of the moving downburst are based on the impinging jet model.The wind field of moving downburst is simulated by an impinging jet device with a movable nozzle.Three dimensional turbulent wind speed is measured by using a three dimensional wind velocity probe from a cobra 3D anemometer,and revealed the time-varying characteristics of the wind velocity in the field of moving downburst.A shock jet device with movable nozzle is used to generate moving downward outflow,and a rigid pressure measurement model of high-rise building is set up at different lateral positions from the centerline of the storm moving center.The influence of storm motion wind loads of surface on tall buildings is investigated by using the pressure history of measured points.(2)This paper considered the numerical simulation of wind field of moving downburst effects.And the numerical calculation and analysis of wind tunnel are established.The large eddy simulation(LES)method is used to systematically study the transient wind field characteristics of moving downburst.The results are compared with the experimental results,the existing empirical models and the measured records,which turns out to be in good agreement.By numerical simulation,the paper analyzed the transient characteristics of the whole process in the moving downburst from the downdraft to the ground and scatter to all sides in detail.By comparing with stationary down flow,this paper focuses on the characteristics of transient wind speed,transient wind pressure characteristics and time-varying characteristics of moving downburst.The wind field characteristics of downburst are studied for different moving velocity and jet velocity ratio.It is found that the ratio of moving velocity to jet velocity has a great influence on the symmetry of near critical storm wind field and the characteristics of near surface turbulence.(3)This paper studied the numerical simulation of wind load on the surface of tall buildings under moving downburst.And the numerical calculation and analysis of wind tunnel are established.Wind loads of tall buildings at different distances from the moving center line of storm are analysised by using a large eddy simulation under moving downburst.And the results were compared with the experimental results of numerical simulation,which proves the validity of the results of numerical simulation.It also studied the environmental changes of wind field around a building and the wind pressure coefficient distribution on the surface of the building under the moving downburst,as well as the dynamic variation of the wind pressure coefficient on the surface of the building during the whole movement of the storm.It's not difficult to find that when the storm passes through the building,there is a greater positive pressure on the top of the building near the center of the storm moving line,and the storm motion increases the extreme wind load on the building surface compared to the stationary downburst.