TR(BR)-145 : Study of 2-dimensional flow behaviour of river using FESWMS-2DH model

Abstract

Two dimensional (surface water analysis) models also simulate unsteady, irregular, non-uniform and complex flow behaviour and features of flood plain areas, rivers, tributaries and coastal areas at desired precision level. Finite Element Surface Water Modelling System (FESWMS-2DH), which is a modular set of computer programs developed by Federal Highway Administrative of US-Department of Transport(Frohlich,1988), simulates steady and unsteady surface water flow which are essentially two-dimensional in a horizontal plane.

The FESWMS-2DH model uses the St.Venant equations which describe the conservation of momentum and conservation of mass. The model computes Frictional losses using the Chezy's and Manning's equation and the turbulence using the Boussinesq eddy viscosity concept. The kinematic eddy viscosity was evaluated from the shear velocity and flow depth. The effects of wind stress and the Coriolis force included in the model, are optional. The Galerkin finite element method was considered in the model formation to solve the resulting system of differential equations.

In the present study, the FESWMS-2DH model was applied to hypothetical cases having relevance to the real life problems, namely; simple channel, strongly curved channel, island area, flood plain area, meandering channel and single bridge opening, to simulate the significant features of flow The effect of changes in model parameters for different flow conditions were also studied. The results obtained by the model for different flow conditions showed good agreement with the results obtained for similar flow conditions. The two dimensional model was able to reproduce the water surface elevations, velocity field and energy gradients for different flow conditions with desired satisfaction.