Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references. / Microfiche. / xix, 113 leaves, bound ill. 29 cm

A numerical method based on potential flow theory is developed for simulating transient, second-order interactions of ocean waves with large fixed bodies of arbitrary shape in two and three dimensions. The physical problem is represented by a mathematical model composed of a fluid domain bounded by the body surface, the still water surface, the seabed, and a control surface truncating the infinite fluid region. The nonlinear free surface boundary conditions defined on the instantaneous free surface are expanded about the still water level by a Stokes expansion procedure. The flow potential to second order is thereby defined with respect to a time-independent boundary which includes the still water surface, and its solution involves a numerical discretization of an integral equation. With the potential separated into incident and scattered components, the Sommerfeld radiation condition applied to the scattered potential is modified to incorporate a time-dependent celerity to account for the transient and second-order effects. The free surface boundary conditions and the radiation condition are then satisfied to second order by a numerical integration in time. An alternative second-order solution is derived based on a different expansion procedure in which the nonlinear free surface boundary conditions and an integral equation defined on the instantaneous free surface are both expanded by a Taylor series, and terms up to second order are retained. The two approaches give rise to identical first-order problems, but give rise to second-order problems which are apparently different. The discrepancy arises from the second-order integral equation in which additional second-order terms are retained. The physical interpretations and limitations of these terms are explored and their effects on the evaluations of wave forces are assessed. Applications of the present method are made to studies of regular wave diffraction around a fully submerged and a semi-submerged circular cylinder in two dimensions, and around a bottom-mounted surface-piercing circular cylinder in three dimensions. The stability and numerical accuracy of the proposed solution and the treatment of the radiation condition to second order are examined. Comparisons of computed wave forces and runup are made with previous theoretical and experimental results and these indicate favourable agreement. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Este trabalho trata do desenvolvimento de um gerador e absorvedor dinâmico de ondas para ensaios com modelos de estruturas oceânicas em escala reduzida, em tanques que simulam as condições de operação encontradas no mar. Propõe-se um procedimento para o projeto de geradores absorvedores ativos de ondas do tipo placa basculante. O procedimento desenvolvido é aplicado ao projeto de um protótipo com quatro módulos geradores de ondas. O protótipo resultante foi instalado no laboratório do Departamento de Engenharia Naval e Oceânica a fim de ser utilizado pela Escola Politécnica da Universidade de São Paulo no estudo de algoritmos de geração e absorção de ondas. Para a medição de altura de onda, foi desenvolvido um sensor por ultra-som utilizando a técnica de pulso-eco e uma guia de ondas. O sensor, fixado junto ao batedor de ondas, é utilizado para a realimentação do controlador de absorção de ondas. Foram realizados ensaios para sua caracterização e comparação com um sensor capacitivo. Nesses ensaios, o sensor por ultra-som apresentou melhor linearidade e resposta dinâmica do que o sensor capacitivo, além de não necessitar de calibração antes de cada ensaio. Foram realizados ensaios com ondas regulares para a avaliação do desempenho do gerador de ondas e para o levantamento das funções de transferência do motor, da onda progressiva longe do atuador H/S e da onda próxima ao atuador H0/S que considera as ondas evanescentes. Os resultados experimentais apresentaram uma boa concordância com o modelo teórico. / This work aims at the development of a wave generator and dynamic absorber to perform tests with models of oceanic structures in reduced scale, in tanks that simulate operating conditions found in the sea. It is proposed a procedure to design absorbing wavemakers of the flap type. The developed procedure is then applied for the construction of an prototype with four wave generator modules. The prototype was installed in the laboratory of the Naval Architecture and Ocean Engineering Departament, to be used by the Polytechnical School of University of São Paulo in the study of wave absorption algorithms. In order to measure wave heights, it was developed a wave height sensor based on ultrasound, applying the pulse-echo technique and a waveguide. This sensor, attached to the flap of the wave generator, is used as part of the feedback system of the wave absorption controller. Tests for its characterization and comparison with a capacitive sensor had been carried out. In those tests, the ultrasonic sensor had presented a better linearity and dynamic response then the capacitive sensor, moreover it does not need calibration before each test. Tests with regular waves had been carried out for the evaluation of the performance of the wave generator and the determination of the transfer functions of the servomotors, of the progressive wave far of the actuator H/S and the wave next to the actuator H0/S that considers the evanescentes waves. The experimental results had presented a good agreement with the theoretical model.

Este trabalho trata do desenvolvimento de um gerador e absorvedor dinâmico de ondas para ensaios com modelos de estruturas oceânicas em escala reduzida, em tanques que simulam as condições de operação encontradas no mar. Propõe-se um procedimento para o projeto de geradores absorvedores ativos de ondas do tipo placa basculante. O procedimento desenvolvido é aplicado ao projeto de um protótipo com quatro módulos geradores de ondas. O protótipo resultante foi instalado no laboratório do Departamento de Engenharia Naval e Oceânica a fim de ser utilizado pela Escola Politécnica da Universidade de São Paulo no estudo de algoritmos de geração e absorção de ondas. Para a medição de altura de onda, foi desenvolvido um sensor por ultra-som utilizando a técnica de pulso-eco e uma guia de ondas. O sensor, fixado junto ao batedor de ondas, é utilizado para a realimentação do controlador de absorção de ondas. Foram realizados ensaios para sua caracterização e comparação com um sensor capacitivo. Nesses ensaios, o sensor por ultra-som apresentou melhor linearidade e resposta dinâmica do que o sensor capacitivo, além de não necessitar de calibração antes de cada ensaio. Foram realizados ensaios com ondas regulares para a avaliação do desempenho do gerador de ondas e para o levantamento das funções de transferência do motor, da onda progressiva longe do atuador H/S e da onda próxima ao atuador H0/S que considera as ondas evanescentes. Os resultados experimentais apresentaram uma boa concordância com o modelo teórico. / This work aims at the development of a wave generator and dynamic absorber to perform tests with models of oceanic structures in reduced scale, in tanks that simulate operating conditions found in the sea. It is proposed a procedure to design absorbing wavemakers of the flap type. The developed procedure is then applied for the construction of an prototype with four wave generator modules. The prototype was installed in the laboratory of the Naval Architecture and Ocean Engineering Departament, to be used by the Polytechnical School of University of São Paulo in the study of wave absorption algorithms. In order to measure wave heights, it was developed a wave height sensor based on ultrasound, applying the pulse-echo technique and a waveguide. This sensor, attached to the flap of the wave generator, is used as part of the feedback system of the wave absorption controller. Tests for its characterization and comparison with a capacitive sensor had been carried out. In those tests, the ultrasonic sensor had presented a better linearity and dynamic response then the capacitive sensor, moreover it does not need calibration before each test. Tests with regular waves had been carried out for the evaluation of the performance of the wave generator and the determination of the transfer functions of the servomotors, of the progressive wave far of the actuator H/S and the wave next to the actuator H0/S that considers the evanescentes waves. The experimental results had presented a good agreement with the theoretical model.

Dans ce travail de thèse est présentée l’analyse des électroproductions exclusives des mésons f ₀ (980) et f₂(1270) sur le proton. Les données ont été acquises pendant l’expérience e1-6 (2001-2002) avec le détecteur CLAS du Jefferson Lab aux États-Unis, en utilisant un faisceau de 5.754 GeV et une cible de dihydrogène. Nous avons mesuré pour la première fois au monde les sections efficaces réduites différentielles de ces deux processus, dans le domaine cinématique 1.5 < Q2 < 4.3 GeV2 et 0.15< xB < 0.55. Nous proposons une interprétation de nos résultats sur une approche basée sur des degrés de liberté hadronique et la théorie de Regge. Une analyse des données en termes d’amplitudes d’ondes partielles et en terme de moments des distributions angulaires a également été tentée. Enfin, nous avons effectué la calibration des photomultiplicateurs du détecteur central de neutron (CND) pour le détecteur CLAS12. Le CND a été optimisé pour l’étude du processus n-DVCS (Diffusion Compton Profondément Virtuelle du neutron). / We present in this report our results for the exclusive electroproductions of f₀(980) and f₂(1270) off the proton. The data were taken during the e1-6 experiment (2001-2002) with the CLAS detector of Jefferson Laboratory, using a 5.754 GeV beam and a liquid hydrogen target. We have measured for the first time the reduced differential cross sections for these two processes, in the kinematical region 1.5 < Q2 < 4.3 GeV2 and 0.15< xB < 0.55. We propose an interpretation of our results according to a Regge-based model. An alternative analysis of the data in terms of partial waves amplitudes as well as in terms of moments of the decay angular distributions has also been attempted. Finally, we have performed the calibration of the photomultipliers of the Central Neutron Detector (CND), to be installed in the CLAS12 detector. The CND has been optimized for the study of the n-DVCS process (Deeply Virtual Compton Scattering off the neutron).