农业工程学报2016，Vol.32Issue(23)：93-100,8.DOI:10.11975/j.issn.1002-6819.2016.23.013
沟灌地表水流与溶质动力学耦合模拟及验证
Hydrodynamic coupled simulation and validation for surface water flow and solute transport in furrow fertigation
摘要
Abstract
Hydrodynamic coupled model of surface water flow and solute transport can provide a powerful tool for design and management of furrow fertigation system. However, the existing models present the shortcomings such as not introducing bed elevation stochastic distribution, splitting solute advection and dispersion processes, as well as the resultant numerical unstable problem. So the exiting models can not be effectively applied to analyze the performance of furrow fertigation system. To solve this problem, the conservative complete hydrodynamic equation and the advection-dispersion equation were applied to describe the surface water flow and solute transport in furrow fertigation, respectively. The finite-volume approach was applied to spatially discretize these governing equations to obtain good mass conservation ability, and then pseudo-time terms were introduced into the governing equations and the fully implicit time scheme was used to reach unconditional stability. After these operations, the conservative complete hydrodynamic and the advection-dispersion equations were turned into a nonlinear algebraic system with diagonal dominance. The Picard iteration approach was introduced to obtain the linearization of this nonlinear algebraic system and all physical processes in furrow fertigation were coupled and simulated in hydrodynamic sense. In the numerical solution development, the water free surface gradient term in conservative complete hydrodynamic equation was added with an extra numerical term. At dry surface domain, this extra numerical term and water free surface gradient term could cancel each other, which represented the real physical process that there were some forces on dry surface domain for water and solute. Consequently, the furrow surface water advance/recession processes under bed elevation stochastic distribution can be accurately simulated. Furrow fertigation experiments were performed to validate the proposed coupled model on October 25, 2015 in Yehe irrigation district, located in Shijiazhuang City, Hebei Province. The experiments were divided into 3 groups i.e. full-time, first-half and second-half time fertilizer applications. Each group contained 3 repetitions and thus there were 9 experimental furrows. Ammonium sulphate was selected as fertilizer. During the experiments, ammonium ion could be fast generated and not be combined with other ions, and thus it was monitored to represent solute. During the experiments, furrow surface water advance/recession processes were observed. Meanwhile, at the distance of 0, 30, 50 and 70 m away from furrow upstream end, 4 observation points were distributed in each furrow to observe the solute concentration change. After experiments, the data including furrow surface water advance/recession processes and solute concentration change at all observation points were applied to validate the proposed coupled model. The validation results showed that the proposed coupled model could well simulate the furrow surface water flow and solute transport, and presented very good mass conservation ability. Specifically, the average relative errors between the observed and simulated data by the proposed coupled model were below 5% and 10% for furrow surface water advance and recession processes, respectively. The average relative errors for solute change were below 8%. By contrast, the average relative errors of advance/recession processes by the existing model were from 15% to 20%. The average relative errors for solute change were more than 10%. Additionally, the mass conservation error for the proposed coupled model was below 0.1% and about 2% for the existing model. Thus, the proposed coupled model overcomes the shortcomings of existing models and provides a useful numerical analysis tool for the management and design of furrow fertigation system.关键词
灌水/土壤水分/模型/沟灌施肥/动力学/耦合/无条件稳定Key words
irrigation/soil moisture/models/furrow fertigation/hydrodynamic/coupled/unconditional stability分类
农业科技引用本文复制引用
章少辉,白美健,魏志斌,冯兵楷..沟灌地表水流与溶质动力学耦合模拟及验证[J].农业工程学报,2016,32(23):93-100,8.基金项目
国家科技支撑计划课题 （）
