Study On The Wind Field Characteristics Of The Upper Roof Of Low-rise Buildings In The Coastal Area Of Southern Zhejiang Province

The southeast coast of south zhejiang province is a high incidence of typhoons.In the typhoon disaster,the collapse and damage of houses is an important cause of heavy casualties and economic losses.At the same time,a variety of equipment and towers have been laid on the upper part of some roofs.The wind field on the upper part of roofs is more complex.When typhoon hits,the first thing to be destroyed is usually the facilities on the upper part of the roofs of buildings,followed by the roofs.Therefore,it is necessary and urgent to study the wind field characteristics of roof.In this context,this paper explores the characteristics of the wind field above the roof in the southeast coast of China through field measurement and analysis of the roof wind field.The following conclusions are obtained:(1)the size of roof wind speed has little influence on the average wind direction within the height of 10 m of the roof,which mainly depends on the Angle between the wind and the wall nearby.The downwind turbulence at 4m away from the roof is significantly lower than that at transverse wind direction,which is inconsistent with the general rule.The roof has a great influence on the spatial wind field below 4m.(2)the turbulence of downwind direction and crosswind direction at different heights below 10 m above the roof shows a decreasing trend with the increase of average wind speed.The higher the height,the less the influence of wind speed changes on the turbulence.(3)the wind field Von Karman spectrum above the roof has a better fitting effect on the power spectrum.The fit of if is the best,and the fit of high and low frequency is weaker.(4)in the selection process of wind profile height,the roof as the zero height reference surface is more in line with the requirements of China's norms.As the wind field above the roof is on the profile of turbulence integral scale,the foreign mature empirical formula is not applicable to the roof.(5)the conversion coefficient of 3s time interval gradually increases with the decrease of height.The national specification stipulates that the conversion coefficient at 10 m height is 1.422,10 min and 60 min at 3s,1 and 0.938,respectively.The mean time interval of 3s was significantly greater than the national standard,while that of 60 min was less than the national standard.(6)in terms of turbulence characteristics,the 3s average time interval can better reflect its local characteristics,while the 10 min and 60 min time interval can better reflect its overall characteristics.With the increase of time interval,the turbulivity increases gradually,and the larger the time interval difference is,the more obvious the turbulivity increases.It shows that turbulence and time distance have a great relationship.