蝶形防风网的体型系数和角度风分配系数

Shape coefficients and skewed wind loading distribution factors of butterfly windbreak nets

针对蝶形防风网的风荷载采用天平测力风洞试验方法进行研究,获得不同风向角两种密实度防风网的气动力系数,分析单体和有周围防风网干扰下气动力系数的差异,并将气动力系数与各国规范及文献结果进行对比,最后给出了蝶形防风网的体型系数和角度风分配系数的建议值。研究表明:蝶形防风网气动力系数的雷诺数效应不显著;对于70%密实度的防风网,单体情况下正面风吹的体型系数大于背面风吹,而有周围防风网干扰情况下规律则相反,其原因为有周围防风网干扰情况下背面风吹的兜风效应更显著;防风网体型系数的试验值与AS/NZS规范非常接近;60%和70%密实度防风网体型系数的建议值分别为1.06和1.10,垂直网面的角度风分配系数建议采用风向角的余弦值。

In order to obtain the wind loading on butterfly windbreak nets,force balance testing methods in a wind tunnel were employed.The aerodynamic coefficients of the windbreak nets with two kinds of solidity ratios under different azimuths were obtained.The difference of aerodynamic coefficients between the isolated case and the interference case was analyzed.Then the testing results were compared with those obtained from various countries’specifications and literatures.Finally,shape coefficients and skewed wind loading distribution factors of butterfly windbreak nets were recommended.The results show that the Reynolds effect of the aerodynamic coefficients of windbreak nets is not significant.For the windbreak net with 70%solidity ratio,its shape coefficients in the windward direction are larger than those in the leeward direction for the isolated case,whereas the coefficients in the windward direction are smaller than those in the leeward direction for the interference case.This is almost due to the factor that the wind catching effect will be more significant for the interference case.The testing results of the shape coefficients with different opening ratios are very close to those regulated in the AS/NZS specifications.The shape coefficients of the windbreak nets with solidity ratios of 60%and 70%are recommended to be 1.06 and 1.10,respectively.And the skewed wind loading distribution factors in the vertical direction are suggested to be the cosine function of the wind azimuth.