Simulation of Rapidly Varied Unsteady Flow in Irrigation Canals Using MacCormack-TVD Numerical Method

Creation and propagation of unsteady flow in irrigation canals causes changes in water delivery to canal intakes. Unsteady flow in irrigation canals usually form by operation of check structures. Up to now simulation of unsteady gradually varied flow in irrigation canals has been considered in various researches. Simulation of unsteady gradually varied flow mostly done using available hydrodynamic models, but these models can’t simulate unsteady rapidly varied flow. In this research, using MacCormack numerical method, a numerical model was developed to solve the governing equations for rapidly unsteady varied flows, and the TVD method was used to control unrealistic and non-physical oscillations. The model was developed in MATLAB programming environment to simulate positive waves caused by the suddenly closure of a gate at the end of the E1R1 canal in Dez irrigation network and a hypothetical channel. The results showed that the higher flow in the gate at the moment of gate closure causes the higher numerical solution errors. Also, the results showed that the simulation using MacCormack method would have a large error, but the simultaneous application of the TVD and MacCormack method could reduce the numerical solution errors and simulate the water surface fluctuations according to the reality.