Study On Aerodynamic Control Method Of Wind Loads On Flat-roof Buildings Based On Uncertain Wind Directions

Low-rise buildings are widely used in engineering application.In order to reduce large wind suctions on the roof,researcher have studied the pneumatic control method of roof wind load.Among the passive control methods,the aerodynamic optimization with spoilers are the best.However,most of these optimization measures mainly aimed at one single wind direction instead of considering the uncertainty of the wind direction.This paper proposes an aerodynamic control method that can be applied for multiple wind directions(e.g.wind direction range)at the same time.For different wind direction arranges,the angle of the passive pneumatic control device is adjustable,and the spoiler parameters are optimized by using CFD numerical simulation methods.The main work and conclusions of the paper include:(1)In order to overcome the shortcoming that the present control method with spoilers is only suitable for one fixed wind direction,a spoiler control strategy for a wind direction range is proposed.For the convenience in engineering application,an implementation strategy is proposed,where the rotation angle of the spoiler is adjustable and other parameters of the spoiler are fixed.The reasonable parameters of the spoiler is determined using the CFD simulation,and the interval optimization algorithm with the surrogate model for different wind direction ranges is introduced to determine the optimal rotation angle of the spoiler for each wind direction range.The calculation example of a flat roof building shows the effectiveness of this control method.(2)This paper systematically studied effects of the layout of the spoiler(the distance between the spoiler and the roof is h,the width of the spoiler is b,the angle of rotation is ? and the overhang length is t)on the wind loading reduction on the roof zones and the whole roof.For the windward area of the roof various measures amplify the roof loads,but the area accounts for a small proportion of the roof.For the corner zone of roof,the height ratio(h/H,H is the height of the building eaves)and the rotation angle ? can reduce the wind loads effectively.When the rotation angle ? = 0°,the reduction effects on the loads are the best.As the ratio of the overhang length t to the plate width b ratio and the width ratio(b/a,a is the partition width)increase,the average wind pressure coefficients in amplitude decreases.(3)Different arrangements of the spoiler on the roof can reduce the roof lift with an average reduction rate of 8%.The increase of the width ratio of the spoiler achieves better overall optimization effects.But the wider the width ratio of the spoiler is,the higher the economic cost.The increase in the overhang rate can also effectively increase the overall optimization rate of roof lift.At the wind direction of 0 degree,the maximum optimization rate is 17.8% when the spoiler height ratio is 0.167.The maximum overall lift optimization rate is 16.43% and 14.12% respectively when the spoiler height ratio is 0.056 at the wind direction of 45 degrees and 90 degrees.At the wind direction of the 0 degree,the overall optimization rate reaches a maximum of 14.32% when the spoiler rotation angle is 0°.At the wind directions of the 45 degrees and 90 degrees,the overall lift optimization rate reaches of 15.79% and 17.43% respectively when the spoiler rotation angle is-20°.The research results show that the best spoiler arrangement is that the width ratio is 0.21,the height ratio is 0.056,the overhang rate is greater than or equal to 60%,and the rotation angle is-20°.