白鹤滩水电站峡谷地形区的风特征研究

位居世界第二大的白鹤滩水电站地处金沙江下游峡谷区，频繁的大风给水电站建设和运行带来了严重影响。掌握水电站坝区大风变化规律，评估峡谷地形对风速的作用，有利于基于周围风场监测和预警峡谷区大风。根据水电站及周边观测资料，对坝区风的变化特征和峡谷地形作用进行了分析。(1)峡谷区最高频率的风向和最大平均风速的风向均为顺着峡谷的偏南风或偏北风，且偏北风频率达55%以上，峡谷锁定了流经气流。(2)坝区大风多发生在干季11月—次年5月，且夜间至清晨大风频率比日间高。干季峡谷风效应强，尤其在19时—次日08时。雨季峡谷风效应降低，局地山谷风增强，表现为山风比谷风持续时间长，08时和18时是山风和谷风交替时间。对应干季和夜晚大风频繁，说明峡谷风效应是影响大风的关键因子。(3)通过狭管效应分析马脖子和葫芦口大桥两个站之间的风速关系，表明峡谷地形使马脖子站风速加强为葫芦口大桥站的1.27倍。利用多种拟合方法建立的两站风速关系表明，当葫芦口大桥站为5m·s-1以下低风速，各方法都难以拟合峡谷区的风速，当风速在5.0～11.5m·s-1时，狭管效应对风速拟合最优，准确率超过70%，对11.5m·s-1以上强风速，多项式拟合效果较优，准确率接近65%。

The Variations of Wind over the Valley Topography of Baihetan Hydropower Station

Baihetan Hydropower Station ,the second largest in the world ,is located in a canyon over downstream of the Jinsha River .Frequent windy weather has an important impact on the construction and operation of the hydropower station .Based on the meteorological observation data around the hydropower station and its surrounding areas ,this paper analyzes the variation characteristics of windy weather in the dam area ,and uses the Canyon Wind Index (CWI)to evaluate the impact of terrain effect on the wind . The conclusions of the paper are as follows :(1)The most frequent wind direction and the average wind direction of the maximum wind speed at all stations of the dam area are either southerly wind and northerly wind ,both along the direction of the canyon .The frequency of the northerly wind is higher than that of the southerly wind ,indicating that the canyon terrain locks the direction of air flows .(2)Gales occur most frequently in the dam area in the dry season from November to May .The CWI shows that the effect of valley wind is stronger in the dry season than that in the rainy season .July to September is a transitional season that witnesses the change of the wind field ,and the canyon wind effect is much weakened .The canyon wind effect is an important factor for the gales in the dam area .The daily variation of gale shows that the velocity is higher during the night and in the early morning than that in the rest of the day ,and the canyon wind effect is more significant from 19:00at night to 08:00of the next day in the dry season .(3)The wind velocities of the northerly wind at the sites of Mabozi station and Hulukou Bridge in the dam area is compared ,and the effect of narrow valley topography of the dam area on the wind speed is evaluated .It shows that when the air flow passes through the canyon ,the velocity can be magnified by 1.27times .The effect of narrow canyon can be best fit by the velocities of Mabozi and Hulukou Bridge when the velocity is between 5.0and11.5m·s-1.For high velocities that are more than 11.5m·s-1,however ,the polynormal fit can better reflects the relationship of the velocities between the two sites.