Analyzing of Flow in Open Channels Networks Using HEC-RAS

Abstract

This article shows a pliable unified modeling scheme applying a materially based, distributed, integrated hydrological and water quality modeling organization. It is need to analyze the unsteady flow in open channels network is done using the computer packages, because solving the Saint-Venant equation is very difficult and sophisticated spatially for a network of channels. The unsteady flow can be analyzed by Saint-Venant equations. These equations can be solved by characteristics and finite difference methods. The HEC-RAS program applies the second method. This program need to data such as: scheme of network channels, geometric properties of cross sections, initial discharge and boundary condition. The outputs of this program are: Surface profiles, flow hydrograph and distribution of flow velocity in each cross section etc. In this research an example was solved in unsteady flow using HEC-RAS. In this procedure, the energy and duration equations are decided for steady, slowly diverse flow by the Newton-Raphson procedure and the offered methodology is used to tree-type and looped-channel networks. An algorithm is introduced to define numerous critical depths in a compound channel. Corrections in channel geometry are provided to prevent the incidence of, many critical depths. The incidence of only one critical depth in an implicate cross section with improved geometry is shown for a tree-type channel network.