Study On Structural Form Optimization Of Orifice Energy Dissipation Well In Water Conveyance Project With Pressure Pipeline

As a common form of energy dissipation,energy dissipation wells are widely used in drainage tunnels and pressurized water pipeline projects.For the energy dissipation wells in the pressure water pipeline,the deep tube type is mostly used at present.For some projects,due to the limitation of topography and geological conditions,it is not possible to carry out large excavation depth,and it is not convenient to arrange the deep tube type energy dissipation wells.In this paper,a kind of energy dissipation well with orifice plate arranged in the longitudinal direction is proposed.The structural form is optimized by numerical simulation method,and the basic law of energy dissipation is further studied.The research results have guiding significance for the design of energy dissipation wells in pressure pipeline water conveyance projects,and also have certain reference value for other similar projects.In this paper,the RNG k-ε turbulence model and the VOF method that tracks the free surface are used to construct a three-dimensional flow mathematical model of the energy dissipation well of the pressurized water pipeline,and the mathematical model is verified by the measured data of the physical model test.Secondly,three types of energy dissipation wells with orifice plates of type Ⅰ,type Ⅱ and type Ⅲ are designed.The energy dissipation wells are composed of closed section and open section,and three energy dissipation orifice plates with different arrangement forms are set in the closed section.Thirdly,using the established mathematical model,the water flow in different forms of orifice energy dissipation wells is numerically simulated,and the water surface flow pattern,near-bottom velocity distribution,turbulent kinetic energy distribution and energy dissipation efficiency of the energy dissipation wells are analyzed.The type Ⅲ orifice energy dissipation well structure with the best energy dissipation effect is selected as the optimal form,and the length of the energy dissipation well is further optimized.The length of the type Ⅲ orifice energy dissipation well is 14D(D is the diameter of the energy dissipation well inlet pipe).Finally,the energy dissipation law of the orifice plate energy dissipation well after structural optimization is preliminarily explored.The research shows that the energy dissipation efficiency of the energy dissipation well decreases with the increase of the flow rate,and the flow parameter Q+does not decrease after reaching 0.5.The energy dissipation efficiency decreases with the increase of the outlet pressure of the outlet pipe.When the outlet pressure of the outlet pipe is 5 kPa,the energy dissipation efficiency is above 70%.When the outlet pressure of the outlet pipe is 20 kPa,the energy dissipation efficiency is above 40%.The head loss coefficient of the energy dissipation well decreases with the increase of the flow rate,and has nothing to do with the outlet pressure of the outlet pipe.When the flow parameter is greater than 0.5,the head loss coefficient gradually stabilizes at about 10.0.According to the numerical simulation results,the empirical relationship between the energy dissipation efficiency of the orifice plate energy dissipation well,the flow parameter Q+ and the outlet pressure parameter p+is obtained by data fitting.The empirical relationship between the head loss coefficient ζ and the flow parameter Q+is obtained.