14:00
Hydrodynamics in Ocean IV
Chair: Rickard Bensow
14:00
30 mins
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EFFECTS OF ROD GROUPS OF DIFFERENT STIFFNESS ON REGULAR WAVE PROPAGATIONAND TURBULENCE CHARACTERISTICS
Chao Tan, Bensheng Huang, Da Liu, Jing Qiu
Abstract: Abstract: The bending elastic modulus was measured using a conceptual plant model comprising groups of silica-gel rods of different stiffness. The effects of the different groups on the regular wave velocity distribution, turbulence characteristics and wave dissipation were studied in a laboratory experiment. The experimental results show that when a wave passed through a group of flexible rods, the velocity period changed gradually from unimodal to bimodal, and the secondary wave peak was more obvious for lower rod stiffness. Furthermore, the turbulence intensity increased with the rod stiffness. With an increase in the bending elastic modulus of the rod group, the wave dissipation coefficient increased. The increase in the wave dissipation coefficient with the bending elastic modulus was not linear but sensitive within a certain range of the elastic modulus.
Key words: rod groups of different stiffness, bending elastic modulus, velocity distribution, turbulence intensity, wave dissipation effect
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14:30
30 mins
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PARAMETRIC HYDRODYNAMIC ANALYSIS OF A MOORED FLOATING STRUCTURE FOR COMBINED WIND AND WAVE ENERGY EXPLOITATION
T.P. Mazarakos, D.N. Konispoliatis, S.A. Mavrakos
Abstract: This paper describes a geometrical parametric hydrodynamic analysis of a multi–purpose floating structure suitable for offshore wind and wave energy sources exploitation. The floating structure is supporting a 5 MW Wind Turbine (W/T) and encompasses an array of hydrodynamically interacting Oscillating Water Column (OWC) devices. Theoretical analysis for such types of floating supporting structures which more realistically allow the renewable electricity generation from the combined wind and wave action have been reported in the literature ([1], [2]).
Based on the theoretical studies on multiple body floating systems reported in recent years ([3], [4]) the numerical implementation involves the hydrodynamic modelling of the floater through an analytical method that accounts for the hydrodynamic interactions among adjacent floating OWC’s, by properly composing the solutions of the diffraction, the pressure– and motion– dependent radiation problems around the floating structure. Moreover, the mooring modelling, the aerodynamic modelling of the rotor, the elastic modelling of the turbine components, namely the blades, the drive train and the tower should be taken into consideration.
Details on the design of the floating structure are discussed and numerical results are obtained through the developed solution on the frequency domain. The absorbed wave power by the structure is presented as a function of the geometric characteristics of each OWC and their placement against the wave front.
REFERENCES
[1] Aubault, A., Alves, M., Sarmento, A., Roddier, D., Peiffer, A. 2011: “Modeling of an oscillating water column on the floating foundation WINDFLOAT”, Proceedings, 30th OMAE 2011, Rotterdam, The Netherlands.
[2] Mazarakos, T., Konispoliatis, D., Manolas, D., Voutsinas, S., Mavrakos, S. 2015: “Modelling of an offshore multi-purpose floating structure supporting a wind turbine including second-order wave loads”, Proceedings, 11th EWTEC 2015, Nantes, France.
[3] Nader, J–R., Zhu, S–P., Cooper, P., Stappenbelt, B. 2012: “A finite – element study of the efficiency of arrays of oscillating water column wave energy converters”, Ocean Engineering, Vol. 43, 72–81.
[4] Mazarakos, T., Konispoliatis, D., Manolas, D., Voutsinas, S., Mavrakos, S. 2015: “Coupled hydro-aero-elastic analysis of a multi-purpose floating structure for offshore wind and wave energy sources exploitation”, Proceedings, 12th STAB 2015, Glasgow, UK.
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