Computation And Application Of Unsteady Flow In Main Irrigation Canal

In the process of water distribution and transportation for irrigation area, changes of water supply leads to the operations of control mechanism of dynamic on control buildings of irrigation canal to realize flow regulation for user’s requirement.After the regulation for water flow,it can change from one steady state to another one,through transient process of unsteady flow.By systematic argument for theory of open channel unsteady flow, the governing flow equations for irrigation channels are made clear, which becomes the construction foundation of numerical flow model.Saint Venant equations and the Preissmann implicit finite difference scheme are used to build the numerical model for both steady flow and unsteady flow of open channel. The nonlinear algebraic equations obtained under stesdy flow are solved by simple iteration method,which is simpler,comparison with other solution methods for water surface computation. The nonlinear algebraic equations obtained under unstesdy flow are solved by Newton-Raphson iteration method. The linear algebraic equations obtained are solved by the method of direct triangle desolvation.Compond inner boundary conditions,such as division mouth,gate flow and flow over weir are considered.It is easy to extend to include more complex type of inner boundary conditions in the model.The numerical model built is applied to the main cannal of Liuyuankou Irrigation area,located in Kaifeng region,Henan province.Flow in the main cannal can be simulated under variable operation conditions,such as inflow changes,opening changes of gates,flow rate changes of divisions,and steady flow conditions. The results obtained have a certain reference value for the practical application.At the same time, the foundation is made for the comprehensive flow and control model construction of whole channel system of this irrigation area.