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Articles 1 - 8 of 8
Full-Text Articles in Ocean Engineering
Wind-Wave Misalignment Effects On Multiline Anchor Systems For Floating Offshore Wind Turbines, Doron T. Rose
Wind-Wave Misalignment Effects On Multiline Anchor Systems For Floating Offshore Wind Turbines, Doron T. Rose
Masters Theses
Multiline anchors are a novel way to reduce the cost of arrays of floating offshore wind turbines (FOWTs), but their behavior is not yet fully understood. Through metocean characterization and dynamic simulations, this thesis investigates the effects of wind-wave misalignment on multiline anchor systems. Four coastal U.S. sites are characterized in order to develop IEC design load cases (DLCs) and analyze real-world misaligned conditions. Stonewall Bank, Oregon showed the highest 500-year extreme wave height, at 16.6 m, while Virginia Beach, Virginia showed the highest 500-year wind speed, at 56.8 m/s. Misalignment probability distributions, at all sites, are found to converge …
Design And Testing Of A Foundation Raised Oscillating Surge Wave Energy Converter, Jacob R. Davis
Design And Testing Of A Foundation Raised Oscillating Surge Wave Energy Converter, Jacob R. Davis
Masters Theses
Our oceans contain tremendous resource potential in the form of mechanical energy. With the ability to capture and convert the energy carried in surface waves into usable electricity, wave energy converters (WECs) have been a long-held aspiration in ocean renewable energy. One of the most popular wave energy design concepts is the Oscillating Surge Wave Energy Converter (OSWEC). True to their namesake, OSWECs extract energy from the surge force induced by incident waves. In their most basic form, OSWECs are analogous to a bottom-hinged paddle which pitches fore and aft in the direction of wave motion. Most commonly, OSWECs are …
Simulating The Effects Of Floating Platforms, Tilted Rotors, And Breaking Waves For Offshore Wind Turbines, Hannah Johlas
Simulating The Effects Of Floating Platforms, Tilted Rotors, And Breaking Waves For Offshore Wind Turbines, Hannah Johlas
Doctoral Dissertations
Offshore wind energy is a rapidly expanding source of renewable energy worldwide, but many aspects of offshore wind turbine behavior are still poorly understood and are not accurately captured by low-cost engineering models used in the design process. To help improve these models, computational fluid dynamics (CFD) can provide valuable insight into the complex fluid flows that affect offshore wind turbine power generation and structural loads. This research uses CFD simulations to examine three main topics important to future offshore wind development: how breaking waves affect structural loads for fixed-bottom wind turbines; how platform motions affect power generation, wake characteristics, …
Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson
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 …
A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana
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 …
Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian
Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian
Masters Theses
The influence of symmetry breaking on the flow induced oscillations of bluff bodies in the steamwise direction is studied. First, a series of experiments is conducted on a one-degree-of-freedom circular cylinder allowed to exhibit pure translational motion in the streamwise direction over a range of reduced velocities, 1.4 < U* < 4.4, corresponding to a Reynolds number range of 970 < Re < 3370. Two distinct regions of displacements were observed in reduced velocity ranges of 1.6 < U* < 2.5 and 2.75 < U* < 3.85. Measured force coefficients in the drag and lift direction were examined, along with the wake visualization, through the range of reduced velocities, to infer the resulting wake modes. A new Alternating Symmetric (AS) mode was found. This transition from symmetric to AS shedding occurred near the end of the first region of response. Similar tests were run with a square prism in the parameter space of 2.4 < U* < 5.8 and 757 < Re < 1900 over angles of incidence of 0° ≤ α ≤ 45°. A distinct region of lock-in is observed for α = 0°, 2.5°, 5°, 7.5° over 3.2 < U* < 5.4 for α = 0°, and decreasing with increasing α. The wake structures were found to be roughly symmetric for α = 0°, but transitioned towards asymmetry …
Simulating The Hydrodynamics Of Offshore Floating Wind Turbine Platforms In A Finite Volume Framework, Maija Benitz
Simulating The Hydrodynamics Of Offshore Floating Wind Turbine Platforms In A Finite Volume Framework, Maija Benitz
Doctoral Dissertations
There is great potential for the growth of wind energy in offshore locations where the structures are exposed to a variety of loading from waves, current and wind. A variety of computer-aided engineering (CAE) tools, based largely on engineering models employing potential-flow theory and/or Morison's equation, are currently being used to evaluate hydrodynamic loading on floating offshore wind turbine platforms. While these models are computationally inexpensive, they include many assumptions and approximations. Alternatively, high-fidelity computational fluid dynamics models contain almost no assumptions, but at the cost of high computational expense. In this work, CFD simulations provide detailed insight into the …
Vortex-Induced Vibration Of Structures With Broken Symmetry, Banafsheh Seyedaghazadeh
Vortex-Induced Vibration Of Structures With Broken Symmetry, Banafsheh Seyedaghazadeh
Doctoral Dissertations
A bluff body, i.e., an object with a blunt cross-section immersed in cross-flow forms an unstable wake, resulting in the formation of large-scale vortical structures, which induce unsteady forces on the body. If the body is flexible or flexibly mounted, vortex-induced vibration (VIV) results, which can have significant implications for a number of physical systems, from aeolian harps to power transmission lines, towing cables, undersea pipelines, drilling risers and mooring lines used to stabilize offshore floating platforms. VIV has been a major subject of research in recent years. The majority of these studies have focused on symmetric systems in which …