【摘要】 琴键堰是本世纪初提出的新型迷宫堰型,倒悬的设计使其基座大为减小,适合安置在任何坝型上,是一种解决大坝泄洪能力不足的有效方案。尽管实验研究证实了其优越的超泄能力,但是由于实验测量无法区分不同溢流前缘上的泄流量,限制了对其复杂流动特性的认识。本文基于VOF自由面捕捉的全三维紊流数值模拟,对其泄流特性进行分析研究。模拟得到的泄流量与实验非常吻合,低水头时泄流能力几乎与溢流前缘的长度成正比,高水头时逐步下降。获得了琴键堰出水口、进水口及侧向三个溢流前缘上的泄流量,分析了出水口、进水口及侧向泄流在总泄流中所占的比重及泄流效率随水头升高的变化规律,从流态的角度分析了影响泄流效率的机制。研究成果深化了对琴键堰不同溢流前缘泄流特性的认识,指明了琴键堰体型优化的方向。更多还原

【Abstract】 Piano-key weir(PKW) is an innovated labyrinth weir that was proposed at the beginning of this century. It has a greatly-reduced base owing to its overhanging shape, and can be placed on all types of dams. With a super discharge capacity, it is an effective solution to the dams that have an insufficient flood-discharge ability. The excellent discharge capacity of PKWs has been verified by previous laboratory experiments, but the results did not distinguish the contributions of different overflow edges to the total capacity and the corresponding complex flow features are not fully understood yet. This paper presents an analysis on the overflow characteristics of PKWs using numerical simulations of 3D turbulent flows and VOF free-surface capturing. Results show that the simulated discharges agree well with experiments. At low head the discharge capacity increases almost linearly with the length of overflow edge, while at high head it decreases gradually. We obtained the discharges over the outlet, inlet and side edges of the PKW, along with their proportions in the total discharge, analyzed the relationship of discharge efficiency versus head rising, and examined the mechanism of variations in discharge efficiency with flow patterns. This work would deepen our understanding of discharge characteristics of piano-key weirs at different overflow edges and suggest possible directions of optimizing piano-key weir shape.更多还原