Experimental Study On The Influence Of Siphon Pipe Slope To Hydraulic Characteristics Of Gas-liquid Two-phase Flow

This paper studies the influence law of siphon pipe slope variation on the hydraulic characteristics of siphon pipes, combining experimental study and theoretical analysis. It analyzes reasons why two-phase flow characteristics of gas-liquid and gas in obverse and adverse slope siphon pipes change with gradient and deduces a calculation formula of siphon pipe flow rate that takes the effect of gradient into account, combined with experimental data.The experimental study is carried out under a total of 286 working conditions, at 2 installation heights of 4 m and 6 m, 13 water heads from 5 cm to 135 cm and 11 types of gradients. Through the experimental study, the influence law of gradient variation in obverse and adverse slope siphon pipes on gas-liquid two-phase flow phenomenon and flow pattern in pipes is obtained and the influence law of gradient variation on void fraction, stable siphon time, velocity of bubble motion, siphon pipe flow rate and head loss in pipes is revealed. Based on a theoretical analysis, the influence of presence of gas on flow rate and head loss is explored. Results show that in obverse and adverse slope siphon pipes, the influence of presence of gas on flow rate and head loss should not be neglected. When two-phase flow patterns of gas-liquid in pipes are different, the influence mechanisms of presence of gas on flow rate and head loss are different, too. Besides, the size and law of various hydraulic factors in obverse and adverse slope pipes at the same slope angle are compared, to serve as a reference for piping in actual engineering.Theoretical research mainly includes dimensional analysis and numerical fitting, for deducing a calculation formula for tilted obverse siphon pipe water flow rate at different gradients applicable for medium pipe sections. Verification results show that the relative error between the calculated value with obverse slope pipe formula and experimental measured values is controlled within ±7%. The error is small, suggesting that the calculation formula of flow rate at different gradients deduced in this paper has good applicability.