Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi, 712100, China; State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, 610065, China.
State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, 610065, China.
Water Res. 2019 May 15;155:320-332. doi: 10.1016/j.watres.2019.02.056. Epub 2019 Mar 2.
Total dissolved gas supersaturation (TDGS) downstream caused by spill discharge from high dams can easily cause fish to suffer from gas bubble disease (GBD). One potential approach to mitigate the impact of TDGS is at the confluence of a downstream tributary, where the introduction of low-TDG water might provide refuge space for fish. In this study, we carried out a series of flume experimental cases and established a three-dimensional TDGS model at confluences. The formula of the dissipation coefficient of TDGS had been obtained by parts of experiment cases. The other parts of experimental cases were carried out to validate the established TDGS model. The biggest relative error of TDG concentration between the experiment and simulation was -5.7%. The results show that the convergence of tributary water (TDG = 100%) can affect the mainstream water (TDG = 140% ∼ 150%) significantly. The two most obvious features are the presence of the separation zone and secondary flow which become more significant as the flow rate increases. The separation zone area at the bottom is smaller than that at the surface. There are two secondary circulations on transversal planes which decrease as the longitudinal distance increases. In addition, the area below 110% and 120% of TDGS in different planes of different cases were compared in detail. This study can provide scientific basis for the utilization of the low-TDG-saturation region to protect fish from the damage of TDGS at confluences during high dam discharge.
总溶解气体过饱和（TDGS）是由高坝泄水引起的下游现象，容易导致鱼类患气栓病（GBD）。缓解 TDGS 影响的一种潜在方法是在下游支流的交汇处，引入低 TDG 水可能为鱼类提供避难空间。在本研究中，我们进行了一系列水槽实验案例，并在交汇处建立了一个三维 TDGS 模型。通过部分实验案例获得了 TDGS 耗散系数的公式。其余部分的实验案例用于验证建立的 TDGS 模型。TDG 浓度的实验与模拟之间的最大相对误差为-5.7%。结果表明，支流水的汇流（TDG=100%）会显著影响主流水（TDG=140%~150%）。两个最明显的特征是分离区和二次流的存在，随着流速的增加，这两个特征变得更加明显。底部的分离区面积小于表面的分离区面积。在横截面上有两个二次环流，随着纵向距离的增加而减小。此外，还详细比较了不同案例不同平面上低于 110%和 120%TDGS 的区域。本研究可为利用低 TDGS 饱和度区域在高坝泄洪期间保护鱼类免受交汇处 TDGS 破坏提供科学依据。
