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Coupled Dynamic Analysis of Moored Wave Energy Converters in Waves
Başlık:
Coupled Dynamic Analysis of Moored Wave Energy Converters in Waves
Yazar:
Erukulla, Gautami D., author.
ISBN:
9780438115286
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (197 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-11(E), Section: B.
Advisors: Chi Yang Committee members: Juan Cebral; Rainald Lohner; Dhafer Marzougui.
Özet:
Waves have the potential to provide a clean and sustainable source of energy that can be captured and converted into electricity by the Wave Energy Converters (WECs). These devices are designed to operate in extreme sea conditions and are restrained by a mooring system. There exists a strong coupling between the dynamic response of the WEC and the mooring system. An accurate study of the moored WEC requires a coupled analysis that considers the dynamics of the mooring system when computing the dynamics of the WEC. However, the conventional methods of marine design do not fully address the coupling effects of the moored WECs. Therefore, there is need for a further development of coupled analysis methods. The aim of this research is to develop a coupled model to investigate the motion response of moored WEC in waves.
This dissertation work is divided into three stages. In stage one, a computational tool for static and dynamic analysis of mooring cable is developed. The mooring cable considered in this research is treated as an extensible elastic slender rod, and the Slender Rod Theory is thus used to derive the governing equations for the mooring cable dynamics. Touch down effect is modeled with non-penetrating boundary condition that assumes the sea bottom to be flat and elastic. Finite element method is chosen to solve the governing equations. The resulting nonlinear system of equations are solved using Newton Raphson iteration method for static problems. For dynamic problems, the resulting nonlinear system of ordinary differential equations are solved by Adams Moulton time integration method. Validation studies are performed for various mooring systems. The numerical solutions obtained using the developed mooring program show a good agreement compared to analytical solutions, experimental data, and MAPS mooring program [1].
In the second stage, a numerical wave tank is developed, and fluid structure interaction simulations are performed, using open source Computational Fluid Dynamics (CFD) solver OpenFOAM. The incompressible Euler/Navier-Stokes equations are solved using a finite volume method on unstructured polyhedral cells. The free surface is captured using the classical Volume Of Fluid (VOF) method. The Navier-Stokes/VOF solver is integrated to a rigid body motion solver, giving it a capability to simulate the motion response of the floating body in waves. The toolbox waves2Foam is employed to generate waves inside the numerical wave tank. Numerical results of the wave tank simulations show a fairly good agreement with those evaluated by the second-order Stokes wave theory. Validation studies of green water impact on a fixed 3D body with and without a vertical wall on the deck are performed to ensure that waves2Foam can simulate highly nonlinear waves. The computed results are compared with the experimental measurements, and the agreements are satisfactory.
Finally, in stage three, a coupled model is developed by integrating the mooring program to the CFD solver OpenFOAM to study the motion response of WECs in waves. Several coupled analysis of a point absorbing type WEC in regular and irregular waves are performed. The buoy of the WEC is modeled as a rectangle with 3 Degree Of Freedom (DOF) in 2D coupled analysis and as a vertical truncated cylinder with 3 DOF in 3D coupled analysis. The surge, heave, and pitch motion response of the WEC subjected to the regular waves is well captured, and the corresponding mooring cable tension cycles are well predicted. When the frequency of the incident waves is close to the resonance frequency of the WEC motion, the WEC undergoes largest motion and thus transfers maximum energy.
The numerical results show that the present coupled model is able to perform the coupled dynamic analysis in the resonance region effectively. Specifically, the amplification of the buoy motion in resonance region is well captured. The coupled model could also successfully simulate the motion response of the cylinder buoy with a linear Power Take Off (PTO) system in regular wave. In addition, the coupled analysis of WEC subjected to bichromatic wave train and JONSWAP wave spectrum have been conducted and reliable results have been obtained. The developed coupled model is employed to study the motion response of WEC in a regular wave for different cable pretensions. The motion response of the rectangle buoy and the cylinder buoy restrained with a multi-catenary system is investigated using the present model. Thus, it can be stated that the coupled model developed in this study can successfully simulate the dynamics of the moored WEC in waves, which is of practical importance to the study of the mooring cable effects and the design of the effective and efficient WEC.
Notlar:
School code: 0883
Konu Başlığı:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(692544.1) | 692544-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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