شبيه سازي جريان ناپايدار دو بعدي آب بطرف زهكش ها

Simulation of two-dimensional transient flow to drainage ditches

The present research suggests a mathematical model for predicting water table position between two underground drainage ditches and simulates a transient flow regime after a single event recharge due to rainfall or irrigation. This model solves the two dimensional transient flow equations within the an isotropic soils for unsteady State. The Alternating Direct Implicit (ADO) method is also used to solve numerically flow equation. The results of comparison indicated that the model is correlated with one-dimensional flow in which vertical hydraulic conductivity of soil was ignored (kz/Kx<<1) (Glover and Dumm). This model was suited to be used for vertical flow condition within the upper and lower line of drainage canal. The results showed that in anisotrope soils in which the vertical hydraulic conductivity is considered (Kz/kx> 1), the use of analytical equation which only horizontal flow towards ditches dose not provide a real water table prediction. The position of water table related to impermeable layer will be overestimated. The position of water table in transient flow using two dimensional flow models has more realistic application than that of analytic procedures.