by Shaun Hurley. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web. / The study presents a reliability-based fatigue life prediction model for the ocean current turbine rotor blades. The numerically simulated bending moment ranges based on the measured current velocities off the Southeast coast line of Florida over a one month period are used to reflect the short-term distribution of the bending moment ranges for an idealized marine current turbine rotor blade. The 2-parameter Weibull distribution is used to fit the short-term distribution and then used to obtain the long-term distribution over the design life. The long-term distribution is then used to determine the number of cycles for any given bending moment range. The published laboratory test data in the form of an ε-N curve is used in conjunction with the long-term distribution of the bending moment ranges in the prediction of the fatigue failure of the rotor blade using Miner's rule. The first-order reliability method is used in order to determine the reliability index for a given section modulus over a given design life. The results of reliability analysis are then used to calibrate the partial safety factors for load and resistance.

Submerged turbines which harvest energy from ocean currents are an important potential energy resource, but their harsh and remote environment demands an automated system for machine condition monitoring and prognostic health monitoring (MCM/PHM). For building MCM/PHM models, vibration sensor data is among the most useful (because it can show abnormal behavior which has yet to cause damage) and the most challenging (because due to its waveform nature, frequency bands must be extracted from the signal). To perform the necessary analysis of the vibration signals, which may arrive rapidly in the form of data streams, we develop three new wavelet-based transforms (the Streaming Wavelet Transform, Short-Time Wavelet Packet Decomposition, and Streaming Wavelet Packet Decomposition) and propose modifications to the existing Short-TIme Wavelet Transform. ... The proposed algorithms also create and select frequency-band features which focus on the areas of the signal most important to MCM/PHM, producing only the information necessary for building models (or removing all unnecessary information) so models can run on less powerful hardware. Finally, we demonstrate models which can work in multiple environmental conditions. ... Our results show that many of the transforms give similar results in terms of performance, but their different properties as to time complexity, ability to operate in a fully streaming fashion, and number of generated features may make some more appropriate than others in particular applications, such as when streaming data or hardware limitations are extremely important (e.g., ocean turbine MCM/PHM). / by Randall David Wald. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

This thesis proposes a sensor approach for quantifying the hydrodynamic performance of Ocean Current Turbines (OCT), and investigates the influence of sensor-specific noise and sampling rates on calculated turbine performance. Numerical models of the selected sensors are developed, and then utilized to add stochastic measurement error to numerically-generated, non-stochastic OCT data. Numerically-generated current velocity and turbine performance measurements are used to quantify the relative influence of sensor-specific error and sampling limitations on sensor measurements and calculated OCT performance results. The study shows that the addition of sensor error alters the variance and mean of OCT performance metric data by roughly 7.1% and 0.24%, respectively, for four evaluated operating conditions. It is shown that sensor error results in a mean, maximum and minimum performance metric to Signal to Noise Ration (SNR) of 48.6% and 6.2%, respectively. / by Matthew T. Young. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

The flow field behavior of axial flow turbines is of great importance, especially in modern designs that may operate at a low Reynolds number. At these low Reynolds numbers, the efficiency loss is significantly augmented compared to higher Reynolds number flows. A detailed incompressible numerical study of a single stage axial-flow turbine at a low Reynolds number is investigated with the use of multiple eddy-viscosity turbulence models. The study includes epistemic uncertainty quantification as a form of numerical error estimation. The numerical results show good qualitative and quantitative agreement with experimental data. It was found that the shear stress transport (SST) k - ω turbulence model with rotation/curvature correction and inclusion of transition modeling is most capable at predicting the mean velocity distribution, which is further enhanced when the URANS formulation is employed. However, all the cases indicate a large variation in the prediction of the root-mean-squared of the turbulent velocity fluctuations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

A finite element tool has been developed to design and investigate a multi-hull composite ship structure, and a hybrid hull of identical length and beam. Hybrid hull structure is assembled by Titanium alloy (Ti-6Al-4V) frame and sandwich composite panels. Wave loads and slamming loads acting on both hull structures have been calculated according to ABS rules at sea state 5 with a ship velocity of 40 knots. Comparisons of deformations and stresses between two sets of loadings demonstrate that slamming loads have more detrimental effects on ship structure. Deformation under slamming is almost one order higher than that caused by wave loads. Also, Titanium frame in hybrid hull significantly reduces both deformation and stresses when compared to composite hull due to enhancement of in plane strength and stiffness of the hull. A 73m long hybrid hull has also been investigated under wave and slamming loads in time domain for dynamic analysis. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

A determinação de características dinâmicas de estruturas aeronáuticas é um assunto extremamente importante na indústria aeroespacial, principalmente devido à demanda contínua para estruturas mais leves e conseqüentemente mais flexíveis. Neste contexto, estruturas aeroespaciais precisam ser submetidas a alguma forma de verificação modal antes do vôo, para assegurar que a aeronave é livre de fenômenos aeroelásticos indesejáveis. Esta análise freqüentemente inclui a identificação experimental de características dinâmicas como freqüência natural, fatores de amortecimento e forma dos modos usando ensaio modal. Neste trabalho foi realizado um ensaio de vibração no solo em uma asa metálica da aeronave Neiva Regente para obtenção das funções resposta em freqüência da estrutura. O método de identificação utilizado para este estudo é o Algoritmo de Realização de Sistemas – ERA. É um método de identificação considerado eficiente e poderoso, pois é capaz de identificar estruturas que apresentem comportamento dinâmico complexo. O algoritmo foi validado através de uma simulação de um modelo hipotético e de dados experimentais de uma viga de alumínio. Os resultados experimentais, porém, apresentam modos computacionais que devem ser eliminados. Para tanto foram utilizados três índices de confiança para qualificar os resultados, sendo estes: Colinearidade de Fase Modal Ponderada (MPCW), Coerência da Amplitude Modal Estendida (EMAC) e Indicador de Consistência Modal (CMI). Os modos que apresentaram melhores índices de confiança são considerados o resultado final do processo de identificação. Desta forma, o processo de identificação foi aplicado para a semi-asa da aeronave Neiva Regente. A identificação revelou-se mais difícil, basicamente devido à complexidade da estrutura somado-se a problemas de ruído, o que levou a um número pequeno de modos identificados / The determination of the dynamic characteristics of aircraft structures has become an extremely important issue in the aerospace industry, primarily due to the continuous demand for lighter and consequently more flexible structures. In this context, most aerospace structural system must be subjected to some form of modal verification prior to flight in order to ensure that the aircraft is free from any dangerous aeroelastic instability phenomena. The verification procedure often includes the experimental identification of structural characteristics such as the natural frequency, damping factors and normal modes using modal testing. In this work, a ground vibration testing (GVT) of a metallic wing of the Neiva Regente aircraft was accomplished in order to assess the frequency response functions. The basic identification method used for this study is the Eigensystem Realization Algorithm – ERA. It is an identification method, which is considered efficient and powerful, because it is capable to identify structures that present complex dynamic behaviour. The algorithm was valited through data obtained from a simulation of a hypothetical model and dynamic measurement accomplished in an aluminium beam. The experimental results, nevertheless, present computacional modes that must be removed from the model. Three confidence factors were used to qualify the results, namely the Modal Phase Collinearity – Weighted (MPCW), Extended Modal Amplitude Coherence (EMAC) and Consistent-Mode Indicator (CMI). The modes that presented higher confidence factor values were considered as the final result of the identification process. Then, the identificatin process was applied to a semi-wing of the Neiva Regente aircraft. This case has revealed a much harder identification procedure, where the complexity of the structure plus noisy data have led to a small number of identified modes

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Bibliography: leaves 97-98. / M.S.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography: leaves 363-373. / Ph.D.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography : leaves 130-132. / M.S.

Thesis. 1975. M.S. cn--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 93-94. / by Hugo Scaletti Farina. / M.S.cn