||Mathematical Model of Water Advance and Flow in Small Earth Channels.
Basset, D. L. ;
McCoo, D. K. ;
||Washington State Univ., Pullman. Dept. of Agricultural Engineering.
||DI-14-31-0001-3848; OWRR-A-053-WASH; 14369,; A-053-WASH(1)
( Ditches ;
Open channel flow) ;
( Irrigation ;
Water flow) ;
Mathematical models ;
Fluid infiltration ;
Partial differential equations ;
Boundary value problems ;
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The objective of this project was the development of a mathematical model of unsteady, spatially varied open channel flow in small earth channels. Furrow irrigation, a notable example of such flow, was used to illustrate the development. During this first year the mathematical basis of the model was prepared. This involved the complete partial differential equations of continuity and momentum written for small earth channels where infiltration into the channel bed depletes the flowing stream. Since the equations cannot be solved in closed form, a procedure was prepared for obtaining approximate solutions by numerical methods. This procedure uses the method of characteristics on a fixed rectangular grid. Description was prepared for the five sets of boundary conditions that can occur in furrow irrigation. A preliminary description of water movement into the channel bed and walls was developed. These and other provisions have been assembled into a model and associated digital computer program which describes the complete furrow irrigation process. Provision is included to describe the disposal of water within and from the channel that will result from given flow conditions. The model is operational and is now being tested and revised as needed. (Author)