高扬程虹吸空化现象数值分析

Numerical Study of High-lift Siphon Cavitations

虹吸技术已被广泛应用于工程实际中,特别是在排除边坡地下水和降低泥石流水动力条件方面有极大的应用价值。边坡中深部地下水的排除需要采用高扬程虹吸管,但在实际使用中,高扬程自平衡虹吸管因易断流而造成虹吸排水失效。利用空化理论,系统分析了虹吸管内气泡产生的机理,并通过流体数值分析软件FLUENT发现自平衡虹吸管内气液两相流动是一个从泡状流向弹状流的转变过程。研究结果表明虹吸管内形成弹状气泡后,增加了虹吸流动中的压力降,导致管顶真空度降低,破坏水流连续性,造成虹吸断流,并影响虹吸的下次启动。

Siphon technology has been widely used in engineering practice. It has great application value especially in draining slope＇ s groundwater and reducing debris flow＇ s hydrodynamic conditions. The drainage of groundwater in middle and deep part of slope requires the use of high-lift siphon. However, the cutoff of high-lift and self-balan- cing siphon causes siphon drainage failures in practical use. In this paper, we analyzed the mechanism of bubble generation in the siphon based on the cavitations theory, and employed the fluid numerical analysis software FLU- ENT to found that the gas-liquid two-phase flow in self-balancing siphon is from bubble flow to slug flow. After slug flow is formed in siphon, the siphon flow pressure drop will increase, resulting in the decrease of vacuum degree in the top of siphon, thus damaging the continuity of water flow and leading to interception of siphon, and finally, negatively affecting siphon＇ s next startup