Numerical Simulation Research Of Pipe Diameter Selection In High-lift Siphon Drainage

Landslide is one of the most common geological disasters, rainfall tends to cause slope groundwater levels rising, and induce landslides. Groundwater impact slope sta bility mainly by softening the soil, increasing the weight of soil and increasing penetra tion force, so you can effectively remove groundwater to prevent landslide. The curre nt drainage measures have disadvantages of complex construction, poor long-term eff ects of drainage and high costs.The siphon drainage technology has the advantages o f deep groundwater discharge, and the construction is simple, low cost, is worthy of promoting in slope Protection Project. In this paper, we present a new approach called slope siphon drainage, this method can achieve deep drainage, have simple constructi on and need low costHowever, high water lift in slope drainage cause low-pressure environment, and flow liquid shows intensive cavitation phenomenon under such circumstance, which fi nally leads to gas-liquid two phase flow patterns. In the intermittent siphon drainage p rocess, with the decline in height difference of the liquid surface on both sides of the s iphon, the flow rate gradually decreased, siphon gas-liquid flow is a process of trans ition from bubbly flow to slug flow,. If not removed promptly, the bubbles will accum ulate at the top of the pipe in the intermittent siphon drainage process of low flow rate, and forming mural flow,which will exacerbate cavitations,the siphon degree of vacu um on the right continues to reduce,siphon phenomenon of continuity will be destroye dand ultimately undermine the entire siphon process. By analyzing two-phase flow pa tterns, only complete slug flow could carry the bubbles off and ensure long-term stabl e operation of the siphon drainage. Adopting VOF model of a computational fluid nu merical software named "FLUENT", we simulated the air and flow patterns in siphon pipes of4mm、5mm.6mm and8mm in diameters. The result shows that:in pipes with diameters of less than5mm, the surface tension plays a major role, forming com plete slug flow; in thoses of larger than6mm, mural slug flow shows. This conclusion had also been proved by physical model tests. Using siphon pipe of4mm in diameter, changing wall roughness and contact angle while doing the numerical simulation,it a lso can form complete slug flow, wall roughness almost does not affect flow patterns, changing the contact angle, the shape of complete slug flow is changed, but does not result in the accumulation of air bubbles.