Abstract: 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-balancing 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 FLUENT 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.

Key words: siphon drainage, cavitations, FLUENT, slug flow, pressure drop