Numerical investigation of filling transients in small-scale pipelines with submerged outlet

An elastic model that combines the dead-end and the orifice at the downstream end is proposed in order to study the hydraulic transients during the rapid filling in small-scale pipelines with submerged outlet. In this model, the unsteady water flow is solved by the method of characteristics, the water-air interface is traced by a shock fitting method, and the air phase is controlled by the polytropic law. The model is validated by a filling test in a pipeline with orifice. Then the proposed model is applied to the filling transient analysis in a small-scale pipeline with submerged outlet. Finally, the effects of the submerged depth of the downstream reservoir on the filling transients are analyzed. This model provides a reasonable approximation of the submerged outlet boundary condition in small-scale pipelines.