Numerical Modelling of Dam Break Analysis

Abstract

The work presented in the dissertation consists of numerical studies of dam break flows. Numerical studies of dam break flows were carried out using Reynolds-averaged Navier-Stokes (RANS) approach in which k– ε model plays an important role for turbulence. The volume of fluid (VOF) was carried out for tracking the free surface. The NS solver uses an Eulerian finite volume method (FVM) along with the volume of fluid scheme for phase interface capturing.
A two-dimensional idealized numerical simulation was performed using computational fluid dynamics (CFD) solver, FLUENT. Based on the results, following observations were made; (i) turbulence modeling does not affect the velocity profile in the upstream reservoir, but has significant influence on the downstream velocity; (ii) the velocity magnitude at a specific location changes with time, but the shape of the velocity profiles remains similar. The validation of the model was not possible due to the unavailability of experimental data set.
The present study aims to present the numerical investigation of dam break flow over initially dry bed with a variation in height of bottom obstacle (sill). The effect of reduction in height of obstacle on velocity and pressure is obtained. This study scrutinized the formation and propagation of negative bore behind the wall. Different aspect of flow such as free surface elevation before and after the initial impact have been studied in depth. The pressure peak due to the water impact on the inclined side of bottom sill has also been analyzed. The significance of time step and grid resolution of model on dam break flow are also discussed. The variation of Froude no over the channel has also been displayed with respect to distance travelled by water.