No description available.

In this study, a three-dimensional two-phase (air and water) numerical solver is applied to investigate free surface flows. The first component aims to improve the overall understanding of the underlying physical mechanisms that occur during the interaction between turbulent hydraulic bores and simple structures. Data collected during large-scale physical experiments based on generating dam-break waves in a horizontal rectangular channel is used for comparing to the numerical results. An extensive sensitivity analysis on numerical parameters including spatial discretization and turbulence models is presented. Quantitative comparisons of numerical and experimental time series of water surface elevations, pressure, and net streamwise force exerted on the structure are used to validate the model. In the in-depth analysis, it is demonstrated that the model is able to simulate the pertinent aspects of the flow behaviour that occur during the interaction with good agreement. The numerical impulsive force generated at initial impact shows excellent agreement with the experimental results, particularly for the larger magnitudes bores considered. Since the numerical model treats the air as an incompressible media, the level of agreement observed between the experimental and numerical results suggests that the compressibility of the air in the leading edge of the bore during the physical testing had no significant effect on the measured impulsive force. The two-phase model was also able to capture the occurrence of a second transient spike in the force exerted on the structure when the initial runup collapsed back onto the incoming flow, trapping a pocket of air in the process. The model was further applied to investigate the effect of an initially quiescent layer of water in the downstream channel section on bore propagation characteristics and the subsequent interaction with the structure. It is demonstrated that for small nonzero values of initial downstream depth a substantial increase in bore depth occurs. However, further increases in the downstream depth did not appear have any significant effects. For the greatest downstream depth simulated, a considerable reduction in the hydrodynamic force is observed as a result of a more rapid closing of the wake that develops on the leeside of the structure. The second component of the study applies the same numerical solver to investigate a novel long wave generation technique for producing laboratory-scale tsunami waves. The concept is based on removing the air from the inside of a tank with a submerged outlet at the upstream end of the basin and releasing the water in a controlled manner. A similar procedure as described above was used to calibrate the numerical parameters to experimentally-measured wave heights and periods. To model the influence of the pneumatic valves mounted on top of the upstream chamber, time-varying pressure boundary conditions are developed to regulate and control the pressure inside the tank. Quantitative and qualitative comparisons of the numerical and experimental results show good agreement and a high potential for the solver to be used for similar investigations. An analysis is performed to improve the existing understanding of the wave formation process. The model is also applied to modify test configurations that influence the waveform for which the results may be used to aid in making operating decisions for future tests or in the design of similar wave generating devices.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21569号 / 理博第4476号 / 新制||理||1642(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 橋田 昌樹, 教授 阪部 周二, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

<p>At present, caused by a large amount of wave energy resources and huge energy capacity, the development and utilization of wave energy have come to be an essential development focus of wave energy manufacturing. The purpose of this research is to simulate the ocean in an offshore environment. A three-dimensional computational fluid dynamics (CFD) model was used to analyze the propagation of ocean waves. The Volume of Fluid (VOF) multiphase model and laminar model were used to analyze wave propagation in offshore conditions. Function Methodology and Mobile Methodology were implemented by applying User Defined Function (UDF) code which characterizes transient velocity profile. The parametric study was performed to analyze how velocity and amplitude change. The models were first validated by comparing them with previous analytical wave solutions. To prevent the reflection of the wave, a damping term was added by using User Define Function to define the viscosity of the water phase.</p>

Tendo em vista a importância das obras portuárias e costeiras no desenvolvimento do país e a complexidade dos fenômenos que regem os Processos Litorâneos, torna-se relevante a utilização de modelos físicos, como os canais de ondas, para otimização destes projetos. Neste sentido, os principais objetivos desta Tese são o desenvolvimento de um sistema de controle para o gerador de ondas do Laboratório de Hidráulica da Escola Politécnica da Universidade de São Paulo - LHEPUSP, capaz de gerar ondas irregulares, baseadas em espectros de energia da agitação, bem como, a partir de um estudo com caso de um molhe de berma, avaliar do ponto de vista técnico o procedimento de dimensionamento de quebra-mares com base no ensaio da estrutura frente a ondas regulares com as características da onda significativa de projeto. Uma das contribuições desta Tese é o novo sistema de controle da geração de ondas do LHEPUSP, que é capaz de gerar ondas regulares, irregulares e randômicas. A outra contribuição, referente ao estudo de caso, permitiu concluir que o emprego de ondas regulares na otimização em modelo físico de projetos de quebra-mares pode levar a dimensionamentos conservadores, e portanto de custo mais alto, principalmente no dimensionamento de obras dispostas em profundidades inferiores aos 10 m, onde foram encontradas diferenças para mais no recuo da estrutura, comparativamente com a ação de ondas irregulares de mesma altura significativa. / Considering the harbour and coastal structures significance for the Country development and the complex Littoral Processes phenomena, is an important requirement the physical models use, like wave flumes, to improve these designs. Following this context, the Thesis main purposes are to develop a wave maker control system for the Laboratório de Hidráulica da Escola Politécnica da Universidade de São Paulo - LHEPUSP wave fume able to generate irregular waves, based on wave energy spectra, and also, from a berm jetty case study, evaluate, from the technical point of view, the breakwater design procedure based on structure tests with design significative regular waves. One of the Thesis contribution is the new wave maker control system for the LHEPUSP wave fume able to generate regular, irregular and randomic waves. The other contribution, about the case study, showed as conclusion that the regular waves use for breakwaters design physical model improvement may suggest conservative results, inducing high cost structures, mainly for those ones in depths lower than 10 m, being observed larger structural backward response differences, comparing with irregular waves action with the same significative height.

Tendo em vista a importância das obras portuárias e costeiras no desenvolvimento do país e a complexidade dos fenômenos que regem os Processos Litorâneos, torna-se relevante a utilização de modelos físicos, como os canais de ondas, para otimização destes projetos. Neste sentido, os principais objetivos desta Tese são o desenvolvimento de um sistema de controle para o gerador de ondas do Laboratório de Hidráulica da Escola Politécnica da Universidade de São Paulo - LHEPUSP, capaz de gerar ondas irregulares, baseadas em espectros de energia da agitação, bem como, a partir de um estudo com caso de um molhe de berma, avaliar do ponto de vista técnico o procedimento de dimensionamento de quebra-mares com base no ensaio da estrutura frente a ondas regulares com as características da onda significativa de projeto. Uma das contribuições desta Tese é o novo sistema de controle da geração de ondas do LHEPUSP, que é capaz de gerar ondas regulares, irregulares e randômicas. A outra contribuição, referente ao estudo de caso, permitiu concluir que o emprego de ondas regulares na otimização em modelo físico de projetos de quebra-mares pode levar a dimensionamentos conservadores, e portanto de custo mais alto, principalmente no dimensionamento de obras dispostas em profundidades inferiores aos 10 m, onde foram encontradas diferenças para mais no recuo da estrutura, comparativamente com a ação de ondas irregulares de mesma altura significativa. / Considering the harbour and coastal structures significance for the Country development and the complex Littoral Processes phenomena, is an important requirement the physical models use, like wave flumes, to improve these designs. Following this context, the Thesis main purposes are to develop a wave maker control system for the Laboratório de Hidráulica da Escola Politécnica da Universidade de São Paulo - LHEPUSP wave fume able to generate irregular waves, based on wave energy spectra, and also, from a berm jetty case study, evaluate, from the technical point of view, the breakwater design procedure based on structure tests with design significative regular waves. One of the Thesis contribution is the new wave maker control system for the LHEPUSP wave fume able to generate regular, irregular and randomic waves. The other contribution, about the case study, showed as conclusion that the regular waves use for breakwaters design physical model improvement may suggest conservative results, inducing high cost structures, mainly for those ones in depths lower than 10 m, being observed larger structural backward response differences, comparing with irregular waves action with the same significative height.

This work uses the photonic filtering properties of Fabry-Perot etalons to show improvements in the electrical signals created upon photodetection of the optical signal. First, a method of delay measurement is described which uses multi-heterodyne detection to find correlations in white light signals at 20 km of delay to sub millimeter resolution. By filtering incoming white light with a Fabry-Perot etalon, the pseudo periodic signal is suitable for measurement by combining and photodetecting it with an optical frequency comb. In this way, optical data from a large bandwidth can be downconverted and sampled on low frequency electronics. Second, a high finesse etalon is used as a photonic filter inside an optoelectronic oscillator (OEO). The etalon's narrow filter function allows the OEO loop length to be extremely long for a high oscillator quality factor while still suppressing unwanted modes below the noise floor. The periodic nature of the etalon allows it to be used to generate a wide range of microwave and millimeter wave tones without degradation of the RF signal.

As the climate crisis draws more concern, research and development in wave energy as a renewable energy source has increased. Devices such as wave energy converters (WECs) are being researched, tested, and implemented to make wave energy a competitive power source. Testing of these devices is limited due to environmental concerns such as weather, location, and other issues. WECs require testing in a marine environment, however, performing testing in the actual environment may be difficult due to weather, access, mounting, and other issues. To eliminate environmental unknowns from testing, a wave simulator device can mimic wave behavior without the need for ocean or river testing. After doing research on wave energy and existing solutions, a wave generator device was conceptualized, designed, and manufactured to be used in Cal Poly’s Fluids Lab. The manufacturing portion was limited by time and funding to a small-scale model of the design which was tested and evaluated as the full-scale model would be. The design concept is a device that moves vertically on the back wall of a tank filled with water where the up and down motion will cause waves to form. The vertical motion is achieved by the device being pushed down and pulled up with a crank slider driven by a motor. The rotational motion produced by the motor is translated to linear motion by the crank slider mechanism. The device is restricted to the vertical motion with linear guide rails and attached to the tank with a structural frame. The scale model replicates this design and its components on a small-scale and is used as a proof-of-concept prototype. Its purpose is to validate the design concept and objective of simulating ocean waves. The validated design concept, proven by the scale design, will be manufactured at full-scale by future Senior Design Project teams at Cal Poly. The wave simulator device will be utilized by Cal Poly students, faculty, or affiliates to test different types of WECs.

No description available.

A number of issues associated with the generation and applications of localized waves are addressed in this thesis. First, the salient characteristic features of two canonical localized wave solutions to the scalar wave equation are discussed. Second, novel azimuthally polarized focus wave mode-type and X wave-type localized electromagnetic fields are derived using a vector-valued spectral approach. Third, all reported experiments dealing with the generation of localized waves are discussed and a concise report on field depth measurements, together with practical implications, is presented. Fourth, new methods for generating X waves in the microwave frequency regime are proposed. Emphasis is placed on increasing the field depth. The proposed new feed scheme increases the field depth as much as 10 times compared to the experimental results reported by Mugnai et al. [2000]. Two modified reflector systems are introduced for the generation of X waves. The first uses an offset launcher reflector configuration. The second uses a Cassagrain reflector system with an integrated circular slit. Finally, future work on electromagnetic X wave generation by means of independently addressable array elements is discussed. / Master of Science