Numerical Simulation of Flows Induced by Dam Break: Trapezoidal Obstacles and Venturi Configurations

The complexity of water flow in open channels increases significantly as the geometry varies, with contractions, expansions, obstructions and slope changes creating nonuniform and undulating free surface profiles. This study aims to simulate such transient flows using the one-dimensional Saint Venant equations, which provide a reliable framework for modeling dam failure scenarios in channels with variable topographies. A numerical model is developed using an explicit finite difference scheme based on the modified Lax-Friedrichs method. The model simulates dam break flows over dry and wet beds, incorporating geometric complexities, such as trapezoidal obstacles and Venturi-like constrictions. Key parameters are investigated, including Courant number, spatial resolution, Manning's roughness coefficient and variations in bed elevation. Validation is carried out by comparing the model with the ideal analytical solution for dam failure, as well as with experimental and numerical results from the literature. In the ideal configuration, the model achieves a relative error of about 1% in water depth. In more complex scenarios, it maintains high accuracy in predicting water depths and flow patterns. These results demonstrate the robustness and effectiveness of the method, making it a valuable tool for hydraulic engineering applications involving flood propagation, obstacle interaction and complex channel design. Keywords: Dam break, Saint Venant, Lax-Friedrichs, Numerical modeling, Complex geometry