Browsing by Author "Moya Abuhadba, Jorge Johnny"

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    Modelos de energía oscura y contraste observacional
    (Universidad de Concepción, 2017) Moya Abuhadba, Jorge Johnny; Arévalo Reyes, Fabiola Andrea; Cid, Antonella; Rubilar Alegría, Guillermo Francisco
    En esta tesis estudiamos escenarios alternativos al modelo Lambda Cold Dark Matter para la evolución del Universo tardío. Usando la métrica de Friedmann-Lemaître-Robertson-Walker en el marco de la teoría de Relatividad General de Einstein, investigamos interacciones cosmológicas lineales y no lineales donde la materia oscura y la energía oscura interactúan, transfiriendo energía de una a otra. En particular, nos centramos en modelos de interacción que poseen solución analítica en función del factor de escala cosmológico. Con el fin de analizar cómo estos modelos ajustan los datos observacionales , usamos criterios desarrollados en teoría de información. En particular nos centramos en dos criterios: el critero de infomación de Akaike y el criterio de información Bayesiano. Estos criterios penalizan a los modelos según el número de parámetros libres que poseen y por cómo ajustan ajustan los datos, permitiéndonos compararlos entre ellos. Para este propósito usamos datos observacionales de: Diferentes compilaciones de Supernovas tipo Ia (Constitution, Union 2, Union 2.1 y JLA agrupado), la función de Hubble H(z), oscilaciones acústicas de bariones. Comparamos los modelos de interacción entre ellos analizando si modelos más complejos (modelos con más parámetros) son preferidos por estos criterios. En nuestros análisis encontramos algunas interacciones viables que alivian el problema de la coincidencia. Además, en algunos de estos modelos la dirección de la transferencia de energía entre materia oscura y energía oscura cambia durante la evolución del Universo. Finalmente, concluimos que de acuerdo a los criterios de información, modelos de interacción con el mismo número de parámetros libres ajustan los datos usados de forma similar, independientemente de la naturaleza de la interacción.
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    Modelos shallow water para la propagación de tsunamis, el impacto sobre la vegetación costera y transporte de sedimento.
    (Universidad de Concepción, 2026) Moya Abuhadba, Jorge Johnny; Bürger, Raimund
    This thesis presents the development of advanced finite volume methods for the simulation of complex free-surface geophysical flows governed by shallow-water-type systems. Although the physical problems studied - tsunami propagation through coastal forests and sediment transport with bed evolution - belong to diferent environmental contexts, they share a common mathematical structure based on depth-averaged balance laws involving non-conservative products. The central objective of this research is to extend the classical Saint-Venant framework to include additional physical processes while preserving the well-balanced and conservative properties required for accurate and stable numerical simulation. The first part introduces a one-dimensional multilayer, non-hydrostatic model for tsunami propagation and its interaction with coastal vegetation. The formulation incorporates drag, inertia, and porosity efects of tree canopies in a vertically resolved manner, which enhances the representation of forest-induced attenuation. The governing equations are solved using a projection method for non-hydrostatic pressure coupled with polynomial-viscosity-matrix finite volume schemes. The resulting approach preserves the well-balanced property and remains robust under dry - wet transitions. The second part focuses on morphodynamic processes through a non-hydrostatic Saint- Venant - Exner-type model that couples hydrodynamics with sediment transport, erosion, and deposition. The formulation includes density variations, gravitational efects, and sediment exchange in non-equilibrium between the fluid and bed layers. Novel well-balanced finite volume schemes, the first is a physically motivated correction of the numerical difusion term for the Rusanov and Harten-Lax-van Leer (HLL), the second one is a new polynomial-viscosity-matrixbased (PVM) scheme, denoted "PVM-2I", that modi es the numerical approximation of the bed evolution equation according to its related characteristic speed. These schemes are developed to capture steady states accurately and prevent spurious erosion in numerical simulations. The third part extends the multilayer non-hydrostatic framework to two-dimensional tsunami modeling. The model describes vertical exchanges, inter-layer viscosity, and vegetation drag in a fully coupled system. The numerical implementation combines path-conservative finite volume methods with semi-implicit treatments of the gravitational source terms, which improve computational eficiency while maintaining stability. Together, these contributions provide a unified computational framework for multilayer, multiphase, non-hydrostatic shallow-water systems. The models developed in this work are physically consistent, numerically stable, and computationally efficient, offering new tools for the study of hydrodynamic and morphodynamic processes in coastal and riverine environments, with applications in environmental engineering and natural hazard mitigation.
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