With the Thoma's assumption, the critical sectional area for flow stability of the downstream throttled surge tank is derived theoretically. The effects of the velocity head and momentum exchange at the Tee junction between the surge tank riser and the tail water tunnel on the critical sectional area of the downstream tank have been analyzed using the Gardel's head loss formula. The study shows that the velocity head has an unfavorable effect on the water level stability in the downstream surge tank while the effect of the momentum exchange is positive. Two effects counteract. Thus the critical sectional area of a downstream throttled surge tank is close to that of a corresponding simple surge tank. However, if the size and shape of a riser are optimized, the area of the downstream surge tank may be further reduced. It is also demonstrated that a downstream throttled surge tank can reduce electricity loss and meet the requirements of stability easily in large flow oscillations compared to a simple downstream tank.

The velocity head and momentum exchange at the T-junction between the surge tank with a riser and the tail water tunnel of hydroelectric powerplants have been introduced by using the Gardel’s head-loss formula. The effects of the velocity head and momentum exchange on the critical sectional area of the downstream tank have been analyzed. With Thoma’s assumption, the critical stable sectional area of the downstream throttled surge tank is derived theoretically. The study shows that the velocity head has an unfavorable effect on water level stability in the downstream surge tank while the effect of the momentum exchange is positive. These two effects counteract. Thus, the critical sectional area of a downstream throttled surge tank is close to that of a corresponding simple surge tank. However, if the size and shape of a riser are optimized, the area of the downstream surge tank may be further reduced. It is also demonstrated that a downstream throttled surge tank can reduce electricity loss and easily meet the requirements of stability in large flow oscillations when compared to a simple downstream tank.

The transient process in the conduits of hydropower stations is a very complicated dynamic procedure coupled with fluid, machines, electricity, and even structure. The current methods used to analyze them separately cannot satisfy the design and the operation requirement of those large underground stations with long conduits. So it is necessary to develop a global physical simulation for the power station transients. As an initial discuss, this article focuses on the introduction of model similarity, model scale and some results about great fluctuation, small fluctuation and hydraulic interference in transient flow experiments.

本文研究工程中某些索状柔系结构在任意铰节点荷栽作用下的稳定平衡形状和张力计算问题。利用虚功原理，导出了描述其稳定平衡形状的状态递推方程式并给出了数值解的迭代计算步骤。若干算例表明：利用本文介绍的理论和计算方法对求解这类问题具有计算精度高、收敛速度快、稳定性好和适应性强的优点，对本文讨论的问题，计算工作量要比有限元法少。

水电站进水口漂浮式拦污排由若干浮箱链接成索状，可简化为柔系平面结构。将水流、风和波浪对拦污排浮箱的作用转化为链节点作用力，然后根据虚功原理导出描述拦污排平衡状态的非线性方程组，并采用迭代方法求得漂浮式拦污排轴线张拉形状和张力数值解。洪江水电站工程实例计算结果表明：拦污排形态和轴向张力分布规律受水流单独或与风、波浪组合作用的影响非常明显，不同运行工况呈现不同的形态，且张力一般呈非均匀分布，岸边支墩反力值大于坝前支墩反力值，张拉形态和张力分布与悬链线理论计算结果差别较大。尤其在不发电泄洪运行工况下，进水口水域主流方向变化显著、流速增大，拦污排将出现非稳定性态，可能产生流体诱发大幅度摆动。