Dam-break flow dynamics over a stepped channel with vegetation

Abstract

In spite of the insistence of a variety of studies on floods triggered by a dam failure, the effects of channel unevenness and vegetation have not been fully explored. Some hydrological aspects, such as the sudden change in the topography of a river section, the density of vegetation, and its influence on flood development, need to be further addressed. Therefore, the present work investigates the complex effects of vegetation and channel’s step on wave propagation during a dam break across a dry downstream channel. The Flow-3d Computational Fluid Dynamics package was used to simulate the flow phenomena during a dam break, adopting different geometric conditions and a densely vegetated area of the downstream channel in the far-field.Three-dimensional flow characteristics were reproduced by solutions of Navier-Stokes equations coupled with the standard volume of fluid to track the evolution of the free surface. The turbulent flow characteristics were represented by different approaches frequently used in the scientific literature.The computational model was optimized and validated using experimental data published in the literature. The results showed that the model had high accuracy in predicting the evolution of the free surface, moving hydraulic jump, flow velocity, and flow regime. In addition, the model was able to predict the formation and development of transitional, rotational, and transverse flows, jet flow, nappe flow, wave breaking, the bore evolution in different directions, and the change of the flow regime under the influence of the channel step and vegetation. Accordingly, the flow fluctuations during dam break, wave attenuation, flow separation, and turbulence structure evolution in the vegetated area were predicted.