Hydraulic Performances And Energy Dissipation Effect In A Compound Tapered-expanding Channel

A new type of emitter with compound tapered-expanding channel is designed.The angle of the water retaining structure of the emitter,the distance between the side wall and the distance between the water-blocking plates are designed as geometric parameters,and the 4-factor and3-level orthogonal experiments were carried out to study its hydraulic performance and energy dissipation effect.The Fluent software was used to simulate the emitter’s hydraulic performance and energy dissipation effect of different schemes.Regression model were established between the structural parameters and the local head loss coefficient by the visual analysis and variance analysis.The results show that the flow index of the emitter is 0.4785～0.5392,and the hydraulic performance is good.The local head loss coefficient in the channel unit is 3.220～12.665 under the pressure head of 15 m,and the energy dissipation effect is good.The Reynolds coefficient Re is 440～2217.The critical Reynolds number Re<995 under the pressure head of 10 m;the distance between the side wall and the distance between the water-blocking plates significantly affect the local head loss coefficient of the emitter,and the regression model between the structural parameters of the emitter and the local head loss coefficient is established,and the regression is better.The results show that:1)Whenα=0.1 is used to test,the triangular water retaining structure R,the side wall distance D₂ and the baffle spacing Z have significant effects on the flow,which is the same as the result of range analysis.The most significant reason for the influence of baffle spacing on the flow is that the baffle spacing directly determines the size of the flow section,and the size of the overflow section has a direct impact on the flow.2)The order of the influence of the geometric parameters on the flow pattern index is as follows:baffle spacing z>side wall distance D₂>triangular water retaining structure R>side wall distance D₁,When usingα=0.1,the triangular water retaining structure R,the side wall distance D₂and the baffle spacing Z have significant effects on the flow rate.3)The results of CFD simulation are less than 5%compared with the test results of the enlarged model.At the same time,the flow pattern index of the physical model is 0.463,which is slightly smaller than the simulation result of 0.493,and the hydraulic performance is slightly better than the simulation results.