Dam break over mobile bed: Characterisation ofthe flow by means of pressure distribution and bed shear stress

Abstract

The study of the pressure distribution within the dam-break flow over mobile bed is very important because it allows to discuss the hydrostatic pressure distribution, which is the main assumption for the validity of the shallow water equations (SWE). Indeed, this assumption is not always valid, especially when the streamlines are not straight and not perpendicular to the gravity acceleration direction. The flow varies abruptly in the first instants of the falling dam-break wave evolution, but it tires towards a stationary motion during time. To better characterize this phenomenon it is important to examine the evolution of each component of velocity vector field and the distribution of the pressure, which is compared to the hydrostatic distribution. Moreover, the present study considers the distribution of pressure linked with the distribution of the shear stress, through the Navier-Stokes equations. The final object of this work is to characterize the dam break experiment over mobile bed by means of forces acting during the event. The dam-break experiment under examination has been performed in a dedicated flume designed at the laboratory of Civil Engineering Department, Université catholique de Louvain. The analysis of this very transient flow it is now possible and more accurate thanks to the application of non-intrusive new techniques, such as PIV.