建筑群不均匀性对拖曳力影响的风洞测压实验

针对建筑群不均匀性缺乏系统的研究方法以及多数处于定性研究的现状,从建筑几何结构的形态学角度出发,采用迎风面积指数、平面面积指数、形状指数和综合非直线系数表达建筑群的不均匀性.风洞实验中采用刚性模型测压的方法进行建筑表面压力的测量,并设计了悬浮实验平台直接测量整个区域所受的拖曳力.实验结果表明,分布在较大平面区域内各建筑的单体拖曳力系数沿风向的变化趋势近似为一条热容模式的衰减曲线;利用有代表性的建筑表面压力测量结果求取的整个区域拖曳力系数和基于拖曳力直接测量的拖曳力系数具有相同的趋势,但普遍大10%~20%;对比可知,地面粗糙度改变对模型表面风压差系数的分布影响不显著,综合非直线系数为1.332 5的工况较1.177 5的工况拖曳力系数减小约17.7%,H型建筑表面风压差系数分布与矩形建筑不同,其对气流的强烈作用造成拖曳力系数约34.6%的增加.

Wind Tunnel Pressure Measurement of Drag Force Effects of Non-Uniform Buildings

There are few systematic studies on non-uniform buildings,and most of them are qualitative researches. From the viewpoint of building morphology,the building nonuniformity is described by the frontal area index,the plan area index,the shape index,and the integrated non-linear coefficient. In the wind tunnel experiments,using a designed floating experimental platform,wind pressures on the rigidity model surfaces and the drag force of the whole area were measured,and then the drag force of the whole area was obtained. The results show that the drag coefficients of a single building in the wind direction show a decaying trend which can be described approximately as an attenuation heat capacity model curve. The predicted drag coefficients of the whole area by measuring wind pres-sures on three representative single buildings show a trend similar to the results obtained from the direct measurements of drag force,and the former results are generally 10%-20%larger than the latter ones. It can also be found that dif-ferent terrain roughness has no significant effect on the distribution of wind pressure difference coefficients on model surfaces. The drag coefficient has an approximate decrease of 17.7% when the integrated non-linear coefficient de-creases from1.332 5 to 1.177 5. In contrast with rectangular shape,H-shape has a different distribution of wind pres-sure difference coefficients on model surfaces,and its intensity influence on flow causes a 34.6%increase of the drag coefficient.