Tesis doctoral de Luit Jan Slooten
The ever-growing complexity of groundwater models calls for the generation of modeling software that is expandable enough to allow developers to implement new functionality at low cost, flexible enough to allow users to define a wide variety of modeling problems, and fast enough to allow modellers to represent complex systems in detail. These three goals are known to be somewhat mutually exclusive; and to make matters worse, the tradeoff between them is not an intrinsic property of the design but depends on technical issues such as the capabilities of compiler and programming language. Hence, the qualtiy of a design cannot be evaluated independently of the constraints set by the implementation environment. these difficulties are explicitly recognized in this thesis. The first chapter is dedicated to exploring these issues, by implementing a common operation in numerical modeling, the multiplication of one matrix with another, in different ways, and by compiling the resulting program with different levels of optimization and different compilers. The programming paradigm for which this was done (object oriented) was selected because of its good reputation for reusable and expandable designs. The language tested (fortran 95) was chosen for its high popularity among hydrogeologists and its excelent performance reputation. the lessons learned in this exercise show that the use of high-level classes that contain or operate over large sets of data comes at a very low price in terms of performance while improving expandability and flexibility. This conclusion was considered in the design of a general-purpose simulation and optimization tool for groundwater problems, also presented in theis thesis. The abstraction on which the implementation is based leads to a class design of which the most important classes are phenomenon (representing a conservation principle as expressed by a partial differential equation, pde), process (representing a contribution to a pde), mesh (a spatial discretization and a numerical method) and solver (responsible for solving the phenomenon equations). the relationships between these classes forms the core of the design; new funcitonality can be implemented by extending these classes. finally, this program is used as a research tool to perform a sensitivity analysis of the hydraulic response of coastal aquifers subjected to ocean tides. The emphasis was on assessing which portions of hydraulic conductivity could be estimated from head measurements in the aquifer and where measurement locations should be placed to maximize the information content of the data. A characteristic length was defined based on the analytical solution of wave propagation in homogeneous infinite aquifers containing constant-density water. For such systems, the most informative head data are located at one characteristic length distance from the coast. However, when a fine parameterization is used, the most informative head measurements are closer to the sea, and the most important parameters are those controlling hydraulic conductivity close to the sea. In two dimensions, the convection cell associated to saltwater intrusion does not afect the response fluctuations of sea level. However, the hydraulic conductivity at the outflow region becomes the most important system parameter.
Datos académicos de la tesis doctoral «An object oriented approach to groundwater optimization and simultation problems«
- Título de la tesis: An object oriented approach to groundwater optimization and simultation problems
- Autor: Luit Jan Slooten
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 09/01/2009
Dirección y tribunal
- Director de la tesis
- Jesús Carrera Ramírez
- Tribunal
- Presidente del tribunal: philippe Ackerer
- lLuis Gil espert (vocal)
- Francisco Javier Elorza tenreiro (vocal)
- Andrés Alcolea rodríguez (vocal)