Francesca Aureli

Numerical simulation and experimental verification of Dam-Break flows with shocks

In this paper experimental results of ID Dam-Break flows are compared with those obtained by means of a mathematical model based on the MacCormack shock-capturing scheme. Care has been devoted to the treatment of the source terms of the equations and to the resolution of shocks. To verify the numerical model under severe test conditions, laboratory experiments have been carried out in which shock formation, reverse flow and wetting and drying conditions in the flow field were induced. Comparison of experimental and numerical results shows a very good agreement, as a whole. The essential validity of the numerical model is then confirmed, even in situations in which St. Venant hypothesis are not completely verified.

A non-uniform efficient grid type for GPU-parallel Shallow Water Equations models

A GPU-parallel numerical model for the solution of the 2D Shallow Water Equations, based on a novel type of grid called Block-Uniform Quadtree (BUQ), is presented. BUQ grids are based on a data structure which allows to exploit the computational capability of GPUs with minimum overheads, while discretizing the domain with non-uniform resolution. Different cases have been simulated in order to assess the efficiency of the BUQ grids. Theoretical and laboratory tests demonstrate that speed-ups of up to one order of magnitude can be achieved in comparison with uniform Cartesian grids. In the simulation of a hypothetical flood event induced by a levee breach in a real 83źkm long river reach, with maximum resolution of 5źm, a ratio of physical to computational time of about 12 was obtained, opening scenarios of quasi real-time 2D simulations in large domains, still retaining a high resolution where necessary. Shallow Water Equations parallel numerical scheme suitable for GPU.Novel Block-Uniform Quadtree (BUQ) grid-type, exploiting the computational capability of GPUs with non-uniform resolution.Very large domain can be simulated (38źkm river reach) with high resolution (2źm).Speed-up of one order of magnitude is achieved, in comparison with Uniform resolution Cartesian Grids.High ratio between physical and computational time which enables real-time simulations.

Validation of single- and two-equation models for transient mixed flows: a laboratory test case

ABSTRACT The numerical simulation of transient mixed flows requires suitable mathematical models that must be validated by comparison with experimental data. For this reason, a simple benchmark test case is proposed in this paper. A laboratory study was carried out in a circular conduit, specifically designed to induce a strong pipe filling bore and repeated regime transitions following the sudden opening of an internal gate. No gates or weirs were installed at the pipe ends, and ventilated conditions were guaranteed. Measurements of both pressure head and velocity are provided as supplementary material. The test case was simulated by using two finite volume shock-capturing schemes: a classic Preissmann slot model, and a recent two-equation model. In both cases, numerical results are in good agreement with experimental data, despite the low pressure wave celerity assumed to minimize spurious oscillations. When realistic celerity values are adopted, the two-equation model appears to be more robust in handling flow regime transitions.