Ocean Engineering Commons^™

Integration Of Inboard Propulsion In Shock Mitigating Membrane Hull Technology, Korrey Rotkiske

Theses and Dissertations

Membrane Hull Technology is a strength based marine vessel design concept that seeks to utilize the in-plane properties of fiber reinforced composites to generate a lighter weight vessel with inherent shock mitigation benefits. MHT has been applied on several Naval crafts yet the design features of inboard propulsion systems have not been addressed. Inboard propulsion systems are a very common form of propulsion used in many types of marine vessels especially larger vessels. This thesis seeks to overcome the inboard engine mounting challenges of MHT which limits use of this technology in the marine industry. The fundamental design elements of …

Numerical Simulations Of Comprehensive Hydrodynamic Performance Of Darpa Suboff Submarine, Kenshiro Takahashi

Theses and Dissertations

A numerical study of the DARPA SUBOFF model using computational fluid dynamics (CFD) has been presented for developing a CFD application procedure to compute the hydrodynamic performance of underwater vehicles, including submarines. Several configurations, such as bare hull, fairwater, sterns, and/or ringwing-appended hulls, were examined for the straight-ahead, steady translation and turning, and self-propelled conditions. A systematic study was conducted to ensure an adequate computational domain expansion and reasonable prism layer mesh properties for solutions independent of the parameters. The hydrodynamic forces exerted on the hull and the appendages were verified and validated in accordance with a published methodology under …

Numerical Modeling Of Shoreline Response To Storm Tides And Sea Level Rise, Akash Sahu

Civil & Environmental Engineering Theses & Dissertations

In this study, an integrated hydrodynamic, wave, and sediment transport modeling approach is developed for predicting the spatiotemporal variation of erosion of a sandy shoreline due to storm surge, wave action, tidal variations, and relative sea level rise (RSLR). The study site is located at the northern most portion of the city of Norfolk, Virginia, and it is of importance to the city, both in terms of tourism and for the protection that it provides for upland properties against storms. The region, in general, experiences the highest rate of RSLR on the U.S. East Coast which should result in high …

Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson

Doctoral Dissertations

The goal of this thesis is to experimentally study the structural dynamics, wake interaction, and fluid forces on the multiple-degree of freedom systems typical of floating wind turbines. Vortex--surface alignment about flexibly-mounted prisms is studied to investigate the response of barges and semi-submersible hulls, and new results pertaining to the galloping response kink for a prism with dual inline--crossflow resonance is presented. Flow--induced oscillations of a spar model free to rotate in 3D space is replicated and observed as 2D figure--eight orbits about the center of the spar. Methods to suppress the flow from exciting the spar are proposed. The …

Advancing Numerical Calculation Of Mixed Sized Sediment Transport And Morphology Change, Irene Margaret Watts

Theses and Dissertations

Numerical modeling of sediment transport and morphologic change has become a powerful tool for studying and working in the coastal zone. Numerical calculation can assist in a broad range of projects from regional sediment management to beach nourishment as well as evaluating environmental aspects of dredging and placement and implications to water quality and turbidity. Success in application of these tools is partially dependent on the quality of characterization of the sediments in the field. These parameters could include grain size, mineralogical composition, specific gravity and fall velocity. Sediment transport formulations are sensitive to the spatial representation of the sediments …

A Coastal Estuarine Ensemble Forecasting System, Peyman Taeb

Theses and Dissertations

This research has been conducted in an effort to reduce the computational costs associated with high-resolution coastal estuarine modeling in ADCIRC. It was proposed that model scalability will be significantly enhanced if the conventional single-domain technique is replaced by a nesting method. Preliminary testing indicated the potential for 50% to more than 80% simulation runtime reduction (depending on the study site) by implementing a nesting technique. Once the concept was proved, the development of an operational, ensemble-based forecasting system, exclusively for the east coast of Central Florida and the IRL system, was implemented. The system, referred to as Ensemble Multistage, …

Global Performance Testing, Simulation, And Optimization Of A 6-Mw Annular Floating Offshore Wind Turbine Hull, Hannah L. Allen

Electronic Theses and Dissertations

Floating offshore wind turbine (FOWT) hull technologies are evolving rapidly with many technically viable designs. However, a commercially dominant architecture has yet to emerge. This thesis presents a methodology for evaluation of the hydrodynamic performance of an annular FOWT hull. This hull shows significant promise from a manufacturing and installation standpoint, but limited performance data exists. This thesis will provide ample documentation on scale model testing of an annular FOWT hull as well as the corresponding numerical validation approach and opportunities for design improvement.

The first portion of this work involves testing a 1/100th-scale model in the Harold Alfond Wind …

Experimental And Numerical Analysis Of The Drag Force On Surfboards With Different Shapes, Omar Lahlou

Theses and Dissertations

The aim of the present study is to define the hydrodynamic resistance of surfboards with different designs. Decreasing the drag acting on a board helps the surfer to attain higher surfing performances. It helps to attain higher speeds and maneuvering for the surfer. In this thesis, theoretical, experimental and computational approaches are used to explain how the drag changes with different surfboard shapes. Four surfboards with varying shapes were towed at different speeds and the resulting force was recorded. Two computational models were developed using Star CCM and Flowsquare to confirm the experimental results. The drag force on the boards …

Feasibility Study And Hydrodynamics Of Transformable Submersible Hydrofoil Trimaran, Yipeng Pan

Theses and Dissertations

It has been the endeavor of naval architects to design innovative hull forms to address the political, socio-economic climate and sustainability around the world. It is imperative that countries be able to protect their sea lanes and coastal zones from surveillance and infiltration from hostile foreign entities. Hence there is a need to develop radically different hull form, which possess the elusive ability and are capable of high-speed. In order to fulfill the idea, the hypothesis envisioned in this thesis is: the Transformable Submersible Hydrofoil Trimaran (TSHT) as an innovative and ground breaking hull form would address the feasibility of …

Membrane Hull Technology Implemented Into A D-Collar Work Boat, Joshua Hagan

Theses and Dissertations

Membrane Hull Technology (MHT) was initially developed for the United States Navy Rigid-Hull Inflatable Boats (RHIB) as an alternative structure design to provide weight savings and shock mitigation. MHT accomplishes this by veering away from traditional hull design and utilizing a grid like system with an increased number of longitudinal stringers and transverse frames with a significantly lower moment of inertia when compared to traditional stringers and bulkheads. The decrease in stiffness allows for increased deflection in the hull during high load events with the added benefit of shock absorption. This technology, developed by Structural Composites Inc., has been successfully …

A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana

Doctoral Dissertations

Floating offshore wind turbines (FOWTs) hold great potential for the renewable energy industry, but capital costs remain high. In efforts to increase FOWT substructure efficiency and reduce costs, this thesis investigates a novel multiline anchor concept in which FOWTs share anchors instead of being moored separately. The goal of this thesis is to evaluate the force dynamics, design, and potential cost reduction of the system. Anchor forces are simulated using the NREL 5 MW reference turbine and OC4-DeepCwind semisubmersible platform, and multiline anchor force is computed as the vector sum of the contributing mooring line tensions. The use of a …

Numerical Study On Seakeeping Performance Of Hydrofoil Assisted Submersible Trimaran (Hast), Yuchen Lin

Theses and Dissertations

The present study focuses on the seakeeping characteristics of Hydrofoil Assisted Submersible Trimaran (HAST). The seakeeping performance is an important part in ship design because it effects the comfort, control, resistance and safety. The motions in wave will reduce the performance of ship which is designed and optimized in calm water. The heave and pitch motions of HAST in calm water and regular waves have been investigated by STAR CCM+, a CFD analysis program. The theory of numerical simulation based on STAR CCM+ has been presented. The basic theory of seakeeping performance studies has been discussed. A series of simulations …

Closed Loop Energy Maximizing Control Of A Wave Energy Converter Using An Estimated Linear Model That Approximates The Nonlinear Froude-Krylov Force, Yaqzan Mohd Yaqzan

Dissertations, Master's Theses and Master's Reports

Wave energy converters (WECs) exploit ocean wave energy and convert it into useful forms such as electricity. But for WECs to be successful on a large scale, two primary conditions need to be satisfied. The energy generated must satisfy the network requirements, and second, energy flow from waves to the grid needs to be maximized. In this dissertation, we address the second problem. Most control techniques for WECs today use the Cummins' linear model to simulate WEC hydrodynamics. However, it has been shown that under the application of a control force, where WEC motions are amplified, the linear model diverges …

Development Of A Fused Deposition 3d Printed Buoy And Method For Quantifying Wave Tank Reflections, Samantha G. Swartzmiller

Dissertations, Master's Theses and Master's Reports

Testing model scale prototypes is integral to the development of wave energy converter (WEC) technology. Model scale WECs are tested in wave tanks where they are subjected to repeatable wave fields. Their presence in water creates radiated waves that eventually reflect off tank walls disrupting the intended wave field. Fabrication of model scale WECs is another developing aspect of tank testing. Often model WECs are built of foam. Additive manufacturing is a promising alternative although the most common method, fused deposition modeling (FDM) 3D printing, does not typically produce waterproof parts. The goals of this work were 1) develop a …

Optimization And Control Of Arrays Of Wave Energy Converters, Jianyang Lyu

Dissertations, Master's Theses and Master's Reports

Wave Energy Converter Array is a practical approach to harvest ocean wave energy. To leverage the potential of the WEC array in terms of energy extraction, it is essential to have a properly designed array configuration and control system. This thesis explores the optimal configuration of Wave Energy Converters (WECs) arrays and their optimal control. The optimization of the WEC array allows both dimensions of individual WECs as well as the array layout to varying. In the first optimization problem, cylindrical buoys are assumed in the array where their radii and drafts are optimization parameters. Genetic Algorithms are used for …

Examination Of Ice Impactor And Mold, Matt Wilson

Williams Honors College, Honors Research Projects

This research project investigates impact and damage response of composite sandwich structures impacted with solid ice at extreme low-temperature. Composite sandwich structures of carbon fiber reinforced polymer sheets lining a polyvinyl chloride foam core are subjected to low-velocity impact at arctic temperatures. This impact will be delivered by a solid ice tool-tip via a drop impact testing machine. Data and test results acquired will be composed into a research report that will be submitted to The University of Akron and published in a scientific journal. This project builds upon the earlier study by Elamin, Li, & Tan (2018).