A numerical method is described to study directional wave effects on large offshore structures of arbitrary shape, based on an extension of linear diffraction wave theory for regular waves. A computer program has been developed to compute loading transfer functions and response amplitude operators and hence the loading and response spectra for both long- and short-crested random waves. Cosine powered directional spreading functions which are independent of frequency have been used to account for the shortcrestedness of waves. Comparisions of the results for long- and short-crested seas show that there is a significant reduction in the loading, and hence in the response, due to shortcrestedness of waves. The probabilistic properties of the components of the loading and response are described. Since the sea surface is assumed to follow a Gaussian distribution, these are also random Gaussian variables. In short-crested waves, the loading and response components occur both in-line and transverse to the principal wave direction. Thus the maximum horizontal loading and response may occur in an arbitrary horizontal direction. An analytical method is developed to describe also the probabilistic properties of the maxima of the components and the maxima of their horizontal resultants. In the present study, results are described for a freely floating box. Comparisons are made with published results and are found to be quite favourable. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Thesis (M.A.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 164-169). Also available on the World Wide Web.

WiFi can provide network coverage for users on land at anytime and anywhere, but on the sea, the wireless communication scenes change dramatically due to the signals are non-existence. Although some techniques (e.g. satellite, undersea fiber, microwave communication) have been used in marine communication, they are either too expensive with very small bandwidth, or too limited in its coverage range. We propose to develop a marine wireless mesh network which is formed by low cost buoyed wireless base stations to provide broadband connectivity for users on the sea. Ocean wave simulation and prediction are key technologies in developing marine mesh network, because marine environments are dramatically different from terrestrial environment. The ocean waves have characteristics of rhythmic oscillations and the line of sight between two communication nodes is often blocked by them. Therefore, we have to develop a new wave-state-aware networking protocol which is suitable for marine environments. Ocean wave simulation technology can simulate this kind of dynamic environments and provide a test platform for the development of marine mesh network. Ocean wave prediction technology can improve the throughput of marine wireless network. Thus, they are indispensable technologies in developing marine mesh network. In this thesis, we designed an ocean wave measurement method, two ocean wave prediction methods, and an ocean wave simulation method. Firstly, we designed an accelerometer-based ocean wave measurement method. It can measure the real time wave height accurately. Secondly, we designed an Elman-neural-network-based ocean wave prediction method for nonlinear waves. It has a higher prediction accuracy than other neural network methods in nonlinear wave prediction. Thirdly, we designed a multiple-linear-regression-based ocean wave prediction method for linear waves. It has a higher prediction accuracy and less time consumption than other methods in linear wave prediction. Finally, we implemented and improved a spectrum-based ocean wave simulation method which is originally proposed by Tessendorf. It can present the movement of ocean waves realistically and in real time. To sum up, above four methods provide an effective test platform and technical support for the development of our marine mesh network. / Master of Science / With the development of wireless communication technology, WiFi has been an indispensable resource for daily work and pleasure. However, in the marine environments, WiFi is not exist. Thus, passengers and workers on the sea are eager for it. We propose to develop a marine wireless mesh network which is formed by low cost buoyed wireless base stations to provide WiFi for users on the sea. Marine environments are dramatically different from terrestrial environments. The ocean waves have characteristics of rhythmic oscillations and the link between two buoys is often blocked. Therefore, the signals are also intermittent. We decided to develop a new wave-state-aware networking protocol to eliminate the harmful effect of this kind of rhythmic oscillations. Ocean wave simulation and prediction are key technologies in developing networking protocol, in which ocean wave simulation technology can simulate the marine environments and provide a test platform for developing networking protocol. Ocean wave prediction technology can improve the network throughput. Thus, they are indispensable technologies in developing marine mesh network. In this thesis, we mainly research three problems that related to ocean waves, they are ocean wave measurement, ocean wave prediction and ocean wave simulation. Ocean wave measurement can tell us the current wave height of a buoy, ocean wave prediction can tell us the future height of a buoy, after we know these information, we can decide whether allow the buoy to send signal. It can not only save energy, but also improve the success rate of communication. Ocean wave simulation can provide us a dynamic environment to test whether our networking protocol works well. To sum up, these methods provide an effective test platform and technical support for the development of our marine mesh network.

Comment générer des courants à partir des vagues ? En s'inspirant de la nature et particulièrement des pompes à impédance, deux systèmes permettant de pomper avec des vagues sont étudiés : la pompe à résonance et les vagues au dessus d'une plaque submergée. Dans cette étude, l'origine de l'écoulement est reliée au terme de transport de masse des vagues dans la couche de surface. Il correspond à la quantité de masse déplacée par les vagues entre la crête et le creux au cours d'une période. Ce terme peut-être amplifié par des changements de bathymétrie et par résonance. Cela permet de créer des zones d'aspiration et donc de générer un courant. Le problème est modélisé par une simple description linéaire potentielle. Un modèle avec dissipation est aussi présenté afin de prendre en compte les effets de dissipation dus au déferlement et au frottement visqueux. Le modèle est comparé à des expériences et des simulations. Il permet de prédire les fréquences intéressantes et la dynamique globale. Ceci permet de comprendre l'origine d'un phénomène de pompage par vague, mais aussi de dimensionner le système à partir d'une théorie simple / How to generate currents from water waves? Inspired by nature original way of pumping in the embryonic heart, two wave pumps are studied in the present thesis: the resonance wave pump directly inspired by the Liebau's pump and the waves above a submerged plate pump. The origin of the observed circulation is linked to the wave mass transport term: it corresponds to the amount of mass advected by the waves in the surface layer. The latter is the domain between the crest and the trough of the waves and is a part of the flow that is not always submerged. It is possible to amplify this surface term by resonance and by varying the bathymetry. The latter enables to generate local suction toward the surface layer and leads to mean circulation. The problem is described using a simple potential theory and a dissipative model is proposed to take into account wave dissipation due to friction and wave breaking. The simplified model is compared to experiments and simulations in both cases. It provides a simple framework to predict the pumps behavior: the interesting frequency range and the strength of the flow. It is also a tool for the design of real life applications

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Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaf 47). Also available online.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 101-102). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 104-109). Also available on the World Wide Web.

Thesis (M.S.)--Naval Postgraduate School, 1983. / Includes bibliographical references (leaves 82-84).