Resumen de Performance assessment of finite volume methods in transient simulations of hydraulic processes
Francisco Javier Fernández Franco
In this thesis, the development of a hydraulic/hydrological numerical simulation model is presented. It considers the coupling of surface-subsurface flows, paying special attention to the interactions among submodels. The surface flow is formulated by means of 2D Shallow Water flow equations and 2D Zero-Inertia flow model and includes hydrological components as rainfall or infiltration. Both models are discretized using a hybrid implicit-explicit finite volume scheme and a full comparison is carried out in terms of accuracy and efficiency in several synthetic and real world applications. The efficiency of the implicit scheme is evaluated in every test case in order to emphasize it as a feasible acceleration technique for certain situations. When rainfall-runoff simulations are considered, a correct estimation of the infiltration water losses is of crucial relevance. With the aim of improving the Green-Ampt infiltration model, a novel technique based on the fractional calculus is combined with the surface flow models, leading to promising improvements in the numerical results. On the other hand, two subsurface submodels are presented in this work: 1) A 2D vertical-averaged groundwater flow model based on Darcy's law and Dupuit approximation. The coupling between surface and groundwater flows takes place in the border connecting the phreatic level with the soil surface, leading to infiltration/exfiltration processes. 2) A drainage model based on 1D Shallow Water equations capable of simulating transient flows in a pipe which can be locally pressurized. The pipe pressurization is estimated by means of the Preissmann slot method. In this case, the coupling with the surface occurs at local points such as manholes, where the exchange surface-sewer flux is calculated. Both subsurface submodels are tested and validated independently with several analytical and experimental cases. Overall, the synthetic, analytical and experimental test cases presented in this thesis point out the good applicability of each submodel and of both coupled models.
