Approved for public release; distribution is unlimited / The purpose of the Littoral Combat Ship is to provide the Navy with an affordable, small, multi-mission ship capable of independent, interdependent and integrated operations inside the littorals. The Littoral Combat Ship will be designed to replace high-value Naval assets when conducting high-end missions such as littoral Anti-Submarine Warfare (ASW), Mine Warfare (MIW) and Anti-Surface Warfare (ASuW) as well as perform low-end missions such as Humanitarian Assistance (HA), Non-combatant Evacuation Operations (NEO) and Maritime Intercept Operations (MIO). In order to accomplish these missions and successfully counter the enemy's littoral denial strategy, the Navy has stated the Littoral Combat Ship must incorporate endurance, speed, payload capacity, sea-keeping, shallow-draft and mission reconfigurability into a small ship design. However, constraints in current ship design technology make this desired combination of design characteristics in small ships difficult to realize at any cost. This thesis (1) analyzes the relationship between speed, endurance, and payload to determine the expected displacement of the Littoral Combat Ship, (2) determines the impact of speed, displacement and significant wave height on Littoral Combat Ship fuel consumption and endurance, and (3) analyzes the implication of findings on Littoral Combat Ship logistics. / Lieutenant Commander, Supply Corps, United States Naval Reserve

In developing designs for high speed vessels, the engineer must account for the response of the ship in the environment while operating at mission essential speeds. This thesis presents a seakeeping analysis of David Taylor Model Basin's Series 64 models scaled to a 2500-ton displacement using the SHIPMO and MATLAB software. It also discusses the current technology associated with high speed vessels (HSV's) and the relation to the US Navy. Series 64 models provided the benchmark for resistance data. To expand upon this well known series, this research develops seakeeping data trends for scaled-up models. SHIPMO allows the user to specify the ship's characteristics and the environmental conditions such as wave specifications and spectrum. Using the output files from SHIPMO, the MATLAB program designed during this thesis, produced contour plots for the models' response in pitch and heave. Seakeeping trends were observed based on the plots and further compared to calculations of the seakeeping rank, R, a formula originally developed by Nathan Bales. The results of the research can be used by engineers in application to the design of small displacement, high speed ships, both monohulls and multi-hulls. / http://hdl.handle.net/10945/1070 / US Navy (USN) author.

This thesis develops a method to analyze the roll response of a vessel during a damaged (flooded) scenario. This was done by developing a time-domain method in which the damaged compartment was flooding while the ship is simultaneously subjected to a seaway. The KRISO containership was used as a test hull and was subjected to three flooding conditions. These flooding conditions involved flooding Hold 5, Hold 3, and Hold 1 separately. Newmark’s Beta method for linear acceleration was used to solve the roll motion of equation in which the hydrodynamic coefficients A44, B44, and C44 were predetermined from linear strip theory for various drafts and trim angles. The roll response in the transient flooding state and the steady state, after flooding ceased (fully damaged state), while in wave action was simulated and plotted. The amplitudes from the initial and damaged steady states were recorded at the given wave frequency and wave amplitude, to generate the roll response amplitude operators for the vessel from wave frequency ω = 0.1 rad/s to ω = 2.1 rad/s. Analysis of the RAO curves revealed that the KRISO was not made significantly more unstable by the flooding, for the conditions that were considered, for nearly all wave frequencies except the natural frequency of 0.5 rad/s.

The accurate prediction of forces and motions on autonomous underwater vehicles (AUVs) operating close to the wavy free surface is imperative to their usefulness as oceanic research and warfare craft. Maneuvering models for underwater vessels are typically constrained to deep water motions where surface effects are negligible; however, a number of modeling assumptions that are applicable for deep water motions become invalid when the vessel is in proximity to the air-water interface. This dissertation investigates several aspects for the inclusion of free surface effects in maneuvering predictions of a shallowly submerged underwater vehicle. A lumped parameter maneuvering model for deeply submerged motion is improved to accommodate depth dependent effects by updating hydrodynamic derivatives using strip theory and boundary element method analysis. This new model can predict near-surface maneuvering motions of an AUV operating in calm or wavy waters. Alternative free surface affected motion predictions are offered by the Lagrangian Nonlinear Maneuvering and Seakeeping (LNMS) model, which provides motion predictions of a vehicle under waves using calculations from first principle energy considerations. While both models provide their own approach to shallowly submerged vehicle motion predictions, each model suffers from its own limiting hydrodynamic modeling assumptions such as linearized free surface boundary conditions, potential flow assumptions, and slowly varying motions. An investigation into the errors from these simplifying assumptions, including under prediction of the steady-state wave making forces and neglect of viscous effects, led to the creation of an innovative impulse motion model for the calculation of hydrodynamic parameters reducing the need for simplifying assumptions. The significant, novel contributions to near-surface AUV maneuvering research provided in this dissertation are listed below: 1. Creation of a free-surface affected lumped parameter maneuvering and seakeeping model using depth corrected hydrodynamic parameters from strip theory and boundary element method analysis 2. Investigation into the errors associated with linearized free surface boundary conditions and potential flow assumptions during the prediction of near-surface steady-state motions 3. Development of an impulse motion simulation procedure using 3D Unsteady Reynolds- Averaged Navier-Stokes Equation (URANSE) solvers to calculate the infinite frequency hydrodynamic added mass of a shallowly submerged underwater vehicle from rest and constant forward speed / Doctor of Philosophy / Autonomous underwater vehicles (AUVS) are an increasingly used tool in the exploration, defense, and study of our oceans and seaways. An essential aspect for the creation of various AUV systems is the accurate prediction of forces and motions while operating in a variety of different conditions, including near the wavy water surface. Maneuvering models that predict the motions of underwater vehicles often opt for deep water simplifying assumptions where the free surface has no effect; however, these assumptions aren't always valid. This dissertation looks to better understand the effects that a free surface has on AUV motion predictions and how these effects can be captured, understood, and incorporated within different maneuvering models. This goal is achieved by updating a previously constructed deep water maneuvering model to account for proximity to the free surface as well as exploring new methods that calculate the hydrodynamic parameters of a vehicle operating at these depths. With these findings, AUVs will be better informed to move as intended while operating in important combat and research zones of the ocean.

CIVINS / The United States Navy has taken a new interest in tumblehome hulls. While the stealth characteristics of these hull forms make them attractive to the Navy, their sea keeping characteristics have proven to be problematic. Normal approximations of sea keeping characteristics using linear differential equations with constant coefficients predict a very stable platform, while observations in model tests show a ship that is prone to extreme roll transients. This thesis examines a simple method of producing a non-linear simulation of roll motion using a tumblehome hull provided by the Office of Naval Research. This research demonstrates the significant difference that a variable restoring coefficient introduces into a hull's seakeeping characteristics. / Contract number: N62271-97-G-0026 / CIVINS

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1977. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 114-116. / M.S.

Catamarans provide vast deck space, high thrust efficiency, and excellent transverse stability, however, in rough conditions they can be susceptible to deck slamming from head seas or bow diving in following seas and a pitch-roll coupling effect that can lead to uncomfortable corkscrew motion under bow-quartering seas. A new class of catamaran called Wave-Adaptive Modular Vessels (WAM-V™) aims to help mitigate oceanic input from the cabin by allowing for the relative motion of components not common to classic catamaran design. This thesis presents a set of multi-body dynamics simulation models created for two active WAM-Vs™ along with analysis on their suspension characteristics. Both models provide conclusive and realistic results, with the final model being validated against on-water testing data from a 12-ft unmanned prototype WAM-V. The first of these simulations serves primarily as a tool to evaluate WAM-V™ response characteristics with respect to a variety of parametric variations. The modeling environment is highlighted along with details of the parametric simulation and how it was created. The results fall in line with our expectations and are presented along with analysis of the sensitivity of each parameter at three longitudinal locations. The final simulation attempts to model the response of a 12-ft unmanned surface vessel (USV) prototype of the WAM-V™ configuration. Testing data is collected, processed, and applied to the model for validation of its prediction accuracy. The results of the sea tests indicate that the simulation model performs well in predicting USV motions at sea. Future considerations for testing WAM-Vs™ can include changes in suspension and mass parameters as well as limiting particular degrees-of-freedom by making their joints rigid. / Master of Science

Cette thèse s’inscrit dans le cadre du 12ème appel à projet du Fonds Unique Interministériel (FUI) lancé par l’Etat au premier semestre 2011. Le projet « EM BILBOQUET » a été colabellisé par les pôles de compétitivité Mer Bretagne, Mer PACA et Tenerrdis. Il consiste en la réalisation d’un nouveau système de génération d’électricité issue du mouvement relatif entre deux corps flottants, mus par la houle. Dans cette thèse, nous nous sommes intéressés au contrôle optimal à appliquer sur la génératrice via les convertisseurs statiques, afin d’extraire le maximum d’énergie de la houle incidente. Dans un premier temps, nous avons établi les équations dynamiques régissant le comportement de la structure dans la houle en adoptant les hypothèses de la théorie potentielle. Pour ce faire, nous avons développé un code de calcul spécifique, basé sur une résolution du problème linéaire de tenue à la mer, par des méthodes dites semi-analytiques. Ce code de calcul permet de déterminer les coefficients hydrodynamiques nécessaires à l’écriture de l’équation dynamique dans le domaine fréquentiel, mais aussi dans le domaine temporel via une modification de la formulation de Cummins. Cette dernière nous permet ainsi, dans un second temps, de formuler le problème de maximisation de l’énergie récupérée comme un problème d’optimisation où la variable à optimiser est le couple résistant de la génératrice. Le problème est résolu en temps réel en adoptant une résolution par algorithme dit à horizon fuyant. / In this thesis, we perform a study on a self-reacting point absorber, project FUI 12 “EM BILBOQUET”, in order to optimise energy extraction from incoming waves. Main researches use seabed for providing reference to a floating body, called buoy. However, as it is well-known that ocean energy is greater far away from the shore, sea-depth becomes a constraint. In this thesis a damping plate attached to a spar keel is proposed to allow the floating body to react against it. Energy resulting from the relative motion between the two concentric bodies i.e. the buoy and the spar is harnessed by a rack-and-pinion, which drive a permanent magnet synchronous generator through a gearbox. In the first part of the thesis we have developed a wave-to-wire model i.e. a model of the whole electro-mechanical chain from sea to grid. To this purpose we have developed our own hydrodynamic code, based on linear potential theory and on a semianalytical approach, solving the seakeeping problem. The hydrodynamic coefficients obtained such as added mass, radiation damping, and wave excitation forces are required for solving the dynamic equation based on Cummins formulation. The second part of the thesis focuses on the self-reacting point-absorber optimal control strategy and the Model Predictive Control (MPC) formulation is proposed. Objective function attempting to optimise the power generation is directly formulated as an absorbed power maximisation problem and thus no optimal references, such as buoy and/or spar velocity, are required. However, rather than using the full-order WEC model in the optimisation problem, that can be time-consuming due to its high order, and also because of the linear assumptions, we propose the use of a “phenomenologically" one-body equivalent model derived from the Thévenin’s theorem.

A capacidade de prever os movimentos de uma plataforma de petróleo sujeita a ondas é bastante importante no contexto da engenharia naval e oceânica, já que esses movimentos terão diversas implicações no projeto deste sistema, com impactos diretos nos custos de produção e tempo de retorno do investimento. Esse trabalho apresenta os fundamentos teóricos sobre o problema de comportamento no mar de corpos flutuantes sujeitos a ondas de gravidades e um método numérico para solução do problema 2D no domínio do tempo. A hipótese básica adotada é a de escoamento potencial, que permitiu a utilização do método de elementos de contorno para descrever a região fluida. Optou-se pela utilização de fontes de Rankine como função de Green no desenvolvimento do método, o qual será abordado somente no contexto linear do problema matemático, delimitado através de um procedimento combinado entre expansão de Stokes e série de Taylor. As simulações são realizadas no domínio do tempo sendo, portanto, resolvido o problema de valor inicial com relação às equações do movimento e equações que descrevem a superfície-livre combinadas com dois problemas de valor de contorno, um para o potencial de velocidades e outro para o potencial de aceleração do escoamento. As equações integrais de contorno permitem transformar o sistema de equações diferenciais parciais da superfície livre num sistema de equações diferenciais ordinárias, as quais são resolvidas através do método de Runge-Kutta de 4a. ordem. As equações integrais são tratadas de forma singularizada e o método utilizado para discretizar as mesmas é de ordem baixa tanto para a função potencial quanto para a aproximação geométrica, sendo as integrações necessárias realizadas numericamente através de quadratura Gauss-Legendre. O algoritmo numérico é testado e validado através de comparações com soluções analíticas, numéricas e experimentais presentes na literatura, considerando os problemas de geração de ondas, cálculo de massa adicional e amortecimento potencial através de ensaios de oscilação forçada, testes de decaimento e, por último, resposta em ondas. Os resultados obtiveram boa concordância com aqueles adotados como paradigma. / The ability to predict the seakeeping characteristics of an offshore structure (such as an oil platform) is very important in offshore engineering since these motions have important consequences regarding its design and therefore its cost and payback period. This work presents the theoretical and numerical aspects concerning the evaluation of the 2D seakeeping problem under the potential flow hypothesis, which allows the use a Boundary Elements Method to describe the fluid region with Rankine sources as Green function. The linearized version of the mathematical problem is built by a combined Stokes expansion and Taylor series procedure and solved in time domain. The initial value problem concerning the motion and free surface equations are solved combined to the boundary value problems considering the velocity and acceleration flow potentials, which transform the partial differential equations of the free surface into ordinary differential equations, that are solved using the 4th order Runge-Kutta method. The integral equations are solved in its singularized version using a low order method both for the potential function and the geometrical approximation, with the terms of the linear system evaluated using Gauss Legendre quadrature. The numerical scheme is tested and validated considering analytical, numerical and experimental results obtained in the literature, concerning wave generation, added mass and potential damping evaluation, decay tests and response to waves. The results achieved good agreement with respect to those used as paradigm.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / by Christopher Graham McMuldroch. / M.S.