基于非恒定渐变流-急变流方程的变流量畦灌数值模型

Simulation Model of Varied-discharge Border Irrigation Based on Gradually Varied Unsteady Flow and Rapidly Varied Unsteady Flow Equations

传统畦灌模型多是基于非恒定渐变流方程建立的,在模拟变流量畦灌水流运动时的精度难以保障。本文综合分析了变流量畦灌过程中田面水流的运动状况,将其按照边界条件的不同划分为恒定流量进水阶段、变流量进水阶段、畦首消退阶段、田面消退第1阶段、田面消退第2阶段等5个阶段,基于非恒定渐变流方程和非恒定急变流方程构建了适用于变流量畦灌系统的渐变流-急变流数值模型,通过2组恒定流量畦灌、4组变流量畦灌的田间试验以及2组文献资料中的畦灌试验数据对模型进行了验证。结果表明,渐变流-急变流畦灌模型模拟值与现场实测结果吻合较好,模拟推进时间决定系数R^(2)均大于0.96、模拟消退时间R^(2)大于0.90。与目前常用的WinSRFR模型相比,渐变流-急变流畦灌数值模型在模拟恒定流量畦灌方面具有相似的精度,且在模拟变流量畦灌方面精度更高。渐变流-急变流畦灌模型可以较精准地模拟变流量畦灌的水流运动状况,可为分析变流量畦灌系统、优化变流量畦灌方案提供支撑。

Traditional surface irrigation simulation models are based solely on the one-dimensional long wave equations,irrespective of the hydraulic performance under the varied-discharge irrigation system.The movement process of surface water flow in varied-discharge border irrigation system was analyzed,which was divided into five stages according to different boundary conditions:constant inflow stage,variable inflow stage,border head recession stage,field surface recession stage 1,and field surface recession stage 2.A numerical simulation model for varied-discharge border irrigation was developed by simulating the border irrigation system of rapidly varied discharge based on the continuity equation and the momentum equation of rapidly varied flow.The proposed model was validated by field experiments with two sets of constant-discharge border irrigation and four sets of varied-discharge border irrigation,as well as two of sets border irrigation experimental data in the literature.It was observed that in all border irrigation experiments,the proposed model reasonably agreed with field measurements.The coefficients of determination values were all greater than 0.96 for the simulated advance times,and greater than 0.90 for the simulated recession times.Compared with the commonly used WinSRFR model,the proposed model had similar accuracy in simulating constant-discharge border irrigation and higher accuracy in simulating varied-discharge border irrigation.The proposed model accurately simulated the inflow movement of varied-discharge border irrigation,thus providing a guarantee for optimizing the design of varied-discharge border irrigation system.