鱼道内过饱和总溶解气体释放规律的试验研究

Experimental Study on Dissipation of Supersaturated Total Dissolved Gas in a Fishway

随着梯级电站的建成运行,总溶解气体(total dissolved gas,TDG)过饱和对鱼类的不利影响受到广泛关注。TDG过饱和水流在库区内的释放速度十分缓慢,上游梯级泄水的不利影响通常会持续到下一梯级坝前。鱼道是恢复河流连通性的重要手段,也是鱼类可能集中分布的区域,TDG过饱和的库区水体作为补给来源可能对通过鱼道的鱼类造成不利影响。本文以自主设计的鱼道型式作为试验水槽,设计开展了不同流量条件下的过饱和TDG输移释放过程试验研究,并根据试验条件开展数值模拟计算,反算得到各条件下的释放系数。结果表明水深是影响过饱和TDG释放的重要因素,过饱和TDG的释放系数随着水深的增大而减小,释放系数与流速、紊动动能、紊动动能耗散率间单因子关系不显著。另外,鱼道复杂的挡板结构使水流流程增长,增加了过饱和TDG释放时间,与无挡板的顺直水槽相比,鱼道内过饱和TDG的释放速度显著提高。该研究为探讨过饱和TDG对过鱼通道内鱼类的不利影响的预测提供参考,同时复杂结构促进过饱和TDG释放的成果也为减缓TDG过饱和不利影响的措施研究提供新思路和参考。

As cascade power stations are constructed and operated,more concerns are attracted to their negative impact on fish from su- persaturated total dissolved gas （TDG） generated by high dam spilling.The supersaturated TDG dissipates very slowly in natural rivers,even more slowly in reservoirs.Generally the spilling flow with high TDG saturation level exists from the upstream cascade＇s stilling basin to the downstream cascade＇s forebay.The fishway,which is an important facility to recover the non-continuity of the river,is a region of fish gathering.The TDG supersaturation flow in the fishway,which uses the water in reservoir as replenishment,is harmful for fishes.To explore the transportation and dissipation of TDG in the fishway,the experimental studies of different flow rates were conducted in a T shape fishway channel.The numerical simulations were performed according to the experimental conditions to obtained dissipation rate of different cases.The results revealed that water depth affected the disspation rate significantly.The dissipa- tion rate of TDG decreased with the increase of water depth in fishway.No clear relations were found between TDG dissipation rate and mean velocity,turbulence and turbulent dissipation rate.Furthermore,it showed that the TDG dissipation rate in fishway was obvi- ously higher than that in channel without clapboards,because the clapboards rose the residence time for flow and TDG in the flow dis- sipated adequately.The research provides scientific basis of the exploration of negative impact to fish in TDG supersaturation flow in fishway,and provides new ideas and reference for the research of the mitigation measures for the problem.