Study On The Influence Of Building Wake On Wind Pressure Characteristics Of High-Rise Buildings Under Downburst

Downburst is a strong downdraft that can cause destructive and strong winds at or near the ground,posing a significant safety threat to structures such as electrical power pylon,bridges and buildings.Studies have been conducted for mutual interference between two identical buildings,and it has been confirmed that the building wake after the building in front of the incoming flow blocking the downburst shock wind will cause some negative pressure effects on the building behind.In real life,there are many low-rise buildings around the high-rise buildings,and the shock wind of the downburst will affect the characteristics of the wind pressure distribution of the high-rise buildings in the back after it acts on the relatively low buildings,and the result will be different from the result of acting on two identical buildings.In this paper,both wind tunnel tests and numerical simulations are used to investigate the above problem,and the research is as follows.(1)The wind field of steady-state downburst is simulated by using boundary layer wind tunnel,and its vertical wind profile is compared with empirical model,experimental data and actual measurement data to verify its reliability.On this basis,building pressure tests were conducted to explore the distribution characteristics of wind pressure coefficients on the surface of disturbed buildings under the effect of the wake of disturbed buildings,and it was found that the middle of the windward side of the disturbed buildings was subjected to larger positive pressure,and the bottom developed to negative pressure.(2)The reliability of the results of the pressure test was demonstrated by numerically simulating the same conditions of the wind tunnel pressure test using the method of large eddy simulation.In order to be closer to the actual downburst,the wind field of downburst is simulated based on the jet model using the same method.And on this basis,the radial distance between the shocking center of the downburst and the disturbed building,the relatively low height of the disturbed building and the building spacing are considered as three typical influencing factors,and the wind pressure coefficient clouds on the surface of the disturbed building and the distribution characteristics of the wind pressure coefficient on the center line and the surround line are analyzed.It is found that with the increase of radial distance,the influence of the average wind pressure coefficient amplification in the middle of building height gradually increases;the increase of building spacing makes the negative pressure enhancement effect at the bottom gradually weaken;and the increase of relatively low disturbed building height makes the development of negative pressure at the bottom of windward side of disturbed building continuously increase along the height;and the intensity of negative pressure enhancement effect remains unchanged.(3)Using UDF to realize the moving characteristics of downburst,we explored the wind pressure coefficient time distribution characteristics of some measurement points on the surface of the disturbed building and compared it with that of a single building,and found that the windward side of the disturbed building was subjected to strongly changing positive and negative pressure effects after the arrival of the downburst shock wind.And the design should consider the stronger alternating positive and negative wind loads in a short period of time,and the strength of the positive and negative pressure effects diminished as the building height increased.The other side of the building,with the continuous movement of the downburst,the transformation from the leeward side to the windward side occurs,and is subject to the positive pressure effect with a larger change.