Behaviour of the Serre Equations in the Presence of Steep Gradients Revisited
For researchers studying dispersive wave models, this provides a detailed numerical characterization of Serre equation behavior under steep gradients, though the findings are incremental.
The study numerically solves the Serre equations for dam-break-like problems with varying initial steepness, identifying four solution structures (two novel) and assessing how well shallow-water wave equations and asymptotic results approximate the Serre solutions.
We use numerical methods to study the behaviour of the Serre equations in the presence of steep gradients because there are no known analytical solutions for these problems. In keeping with the literature we study a class of initial condition problems that are a smooth approximation to the initial conditions of the dam-break problem. This class of initial condition problems allow us to observe the behaviour of the Serre equations with varying steepness of the initial conditions. The numerical solutions of the Serre equations are justified by demonstrating that as the resolution increases they converge to a solution with little error in conservation of mass, momentum and energy independent of the numerical method. We observe four different structures of the converged numerical solutions depending on the steepness of the initial conditions. Two of these structures were observed in the literature, with the other two not being commonly found in the literature. The numerical solutions are then used to assess how well the analytical solution of the shallow water wave equations captures the mean behaviour of the solution of the Serre equations for the dam-break problem. Lastly the numerical solutions are used to evaluate the usefulness of asymptotic results in the literature to approximate the depth and location of the front of an undular bore.