溢洪道闸墩后水翅的水力特性及消减措施研究

Experimental study on hydraulic characteristics and reduction measure of rooster tails behind the pier of the spillway

为研究如何避免溢洪道泄洪过程中,闸墩后生成的水翅会给泄洪安全带来诸多不利的影响。本文利用量纲分析和物理模型试验方法,对溢洪道闸墩后水翅的水力特性和消减措施开展研究。试验结果表明,影响水翅长度和高度的主要因素有闸墩尾部出口处的弗劳德数Fr 0、溢洪道坡度i、闸墩宽度等;在相同泄流条件下,若泄槽坡度变小,水翅长度也随之减小,而水翅高度却相应增加;当弗劳德数Fr 0介于2.3与2.8之间时,闸墩后的水翅长度和高度均显著增大。试验还发现水翅的长度、高度与闸墩后泄流下跌角度α有关,当α增大时,水翅长度和高度也随之增大;当α较小时,水翅现象明显减弱或消失。研究结果为实际工程消除水翅现象提供了新思路,提出的复合式斜尾墩比传统四棱台型尾墩能更好地避免水翅发生,对改善溢洪道、泄洪洞闸墩后的水流流态具有参考价值。

During the flood discharge process of the hydropower project,rooster tails,a kind of hydraulic phenomenon,would happen in the end part for the pier of the spillway and cause adverse effect to the operation of discharge chute.Hydraulic characteristics and reduction measure of rooster tails behind spillway pier are studied by dimensional analysis and hydraulic model test in this paper.The results show that the height and the length of the rooster tails are affected by several factors,including the Froude number Fr 0 of the outlet in the tail part of the pier,the slope ratio i of the spillway,as well as the width b of the middle pier.The length of rooster tails decreases with the decrease of the spillway slope,while the height of the rooster tails increases in the same discharge conditions.When the Froude number Fr 0 is between 2.3 and 2.8,the length and height of rooster tails behind the pier are significantly increased.Moreover,according to the experimental observation,the characteristics of the rooster tails are directly related toα,which is the angle between the water surface concave and the spillway bottom.With the increase of the angleα,there will be a significantly increment of the height and the length of the rooster tails.Finally,a composite sloping-tail pier was designed based on the generation mechanism of the rooster tail,which can effectively eliminate rooster tail and improve the flow pattern behind the pier of the spillway and tunnel.