Comparison Of 2D Numerical Schemes For Modelling Supercritical And Transcritical Flows Along Urban Floodplains

Abstract

Urban floodplains usually have irregular geometry due to different obstacles, urban infrastructures and slope conditions. This may change the flow regime from subcritical to supercritical flow conditions, and vice versa. Implementation of the full momentum equation in 2D shallow water equations (SWEs) is not trivial in mixed flow conditions as subcritical and supercritical flows require different boundary conditions and hence different solution algorithms. Some models ignore the convective acceleration term (CAT) to simplify implementation of the momentum equation for mixed flow conditions. This work tried to investigate the effect of neglecting CATs by testing two 2D models which implement - full SWEs and completely reduced CAT. The models\u27 performances were then tested by setting up hypothetical case studies with changing flow regimes. Simulations results were compared to each other by setting the solutions of the method that solve the full equations as a reference. Findings of the numerical tests showed that, in the cases, results of the model which ignore CATs fully were very similar compared to solutions of the model which implement full SWEs. Hence, simplified models which ignore CATs may be used to model urban flood plains without significant loss of accuracy