垭口地貌要素对风速分布规律影响的风洞试验研究

Wind tunnel test on the influence of col features on wind speed distribution

输电线路微地形气象灾害的调查研究显示,垭口地貌影响下的输电线路风偏闪络事故多发。鉴于垭口地貌不同位置处的风剖面分布规律尚不明确,借助风洞试验,研究了垭口地貌的山丘坡度、谷口宽度等地貌要素对山谷及山脊中轴线上风速分布规律的影响。风洞试验结果表明:与平地风速相比,山谷中轴线及山丘峰顶处风速的最大加速幅度分别达到了33%和53%,明显大于规范规定的10%,容易造成垭口区域内输电线路风偏闪络或倒塔;山谷中轴线风速修正系数随两侧山丘坡度增加而增加,随谷口宽度增加而减小,提出了符合这一规律的计算公式;山谷中轴线上,下风侧风速加速效应略强于上风侧;垭口两侧山丘山顶处风速未受垭口地貌影响,风洞试验测得风速修正系数与单体山丘拟合公式的计算结果基本一致;设计时可统一偏于保守地取用山丘顶部的风速修正系数对平地风速予以修正。

The investigation on meteorological and micro-topography disasters of transmission lines shows that,due to the influence of col,windage yaw flashover and tower failure occurr fre-quently in the mountain region.However,studies on the topography formed by double three di-mension hills are relatively rare,and thus the distribution law of wind profile at different loca-tions is still indefinite.Under this situation,some wind tunnel tests about four types of col mod-el with different hill slopes and different valley widths are carried out.Then,on the analysis of wind tunnel test results,the influence law of some geomorphic features such as hill slope and val-ley width on wind profile is researched in this paper.Finally,some conclusions are derived as fol-lows.Compared with flat land,the degrees of wind speed-up at valley axis and hill peak reach 33% and 53% respectively,which are higher than the 10% stipulated in regulation,tending to cause more windage yaw flashover or tower failures.The wind speed at the valley axis will in-crease with the increasing of hill slope,and decrease with the increasing of valley width.Further-more,an equation matching this regularity is offered.At the valley axis of the col model,the wind speed-up effect of the downwind is a little stronger than the upwind,that may be caused by flow separation and more intensive fluid huddled at the downwind.At the hill peak,col features basically have no influence on the wind speed,so that the wind speed correction coefficients ob-tained by wind tunnel test display a good agreement with those obtained by fitted equation for so-lo hill.Since the wind speed correction coefficients at the hill peak are higher than those at the valley axis,in design the wind speed correction coefficients at the hill peak can be conservatively utilized for the whole col.