Abstract
In the present paper, a numerical and experimental analysis for a wave energy converter under extreme environmental conditions is carried out. After the definition of design waves, including a 100-year return period stochastic sea state and a deterministic rogue wave condition, a numerical analysis using potential theory and a RANS equations solver are compared with experiments carried out at the Seakeeping Basin at the Technical University of Berlin. Results are discussed with special emphasis on the limits of potential theory methods for the evaluation of extreme wave conditions and the use of the presented methodology for early design stages.
Key Words
CFD simulation; experimental hydrodynamics; marine energy; WEC
Address
Ignacio P. Johannesen: School of Engineering, Computing and Mathematics, University of Plymouth, Plymouth, Devon, UK
José M. Ahumada,Gonzalo Tampier and Cristian Cifuentes: Institute of Naval Architecture and Ocean Engineering, General Lagos 2086, Campus Miraflores,
Universidad Austral de Chile Valdivia, Chile
Laura Grüter: Dynamics of Maritime Systems, Technical University of Berlin, Berlin, Germany
Abstract
Tidal stream energy extraction remains a site-specific resource due to the "first generation" criteria requiring high-velocity tidal streams. Most studies on tidal energy and turbine blade design heavily focus on installation sites with higher velocity conditions that are non-existent in tropical countries such as the Philippines. To shorten this gap, this review paper tackles tidal turbine design considerations for low-energetic regions such as the tropics. In-depth discussions of operating principles, methods of analysis, and designs of tidal turbine blades are presented. Notable tidal stream projects around the world are also mentioned in the paper. Also, it provides a perspective on the potential of this renewable energy to produce electricity for various sites in the Philippines. Finally, the paper emphasizes the need for new tidal turbine blade designs to be viable in tropical regions, such as the Philippines.
Address
Mark Anthony Rotor: Department of Mechanical Engineering, State University of New York (SUNY), Korea, 21985 South Korea;
Department of Mechanical Engineering, School of Engineering and Architecture,
Ateneo de Davao University, 8000 Philippines;
Center for Renewable Energy and Appropriate Technologies (CREATe),
Ateneo de Davao University, 8000 Philippines;
Mindanao Renewable Energy R&D Center (MREC), Department of Science and Technology, Philippines
Hamid Hefazi: Department of Mechanical Engineering, State University of New York (SUNY), Korea, 21985 South Korea
Nelson Enano, Jr.: Center for Renewable Energy and Appropriate Technologies (CREATe),
Ateneo de Davao University, 8000 Philippines;
Mindanao Renewable Energy R&D Center (MREC), Department of Science and Technology, Philippines
Abstract
Autonomous Underwater Gliders (AUGs) are a type of Underwater Vehicles that move without the help of a standard propeller. Gliders use buoyancy engines to vary their weight or buoyancy and traverse with the help of the Lift and Drag forces developed from the fuselage and the wings. The Lift and Drag Coefficients, also called Hydrodynamic coefficients (HDCs) play a major role in glider dynamics. This paper examines the effect of the different types of glider fuselages based on the bodies of revolution (BOR) of NACA sections. The HDCs of the glider fuselages are numerically estimated at a low-speed regime (105 Reynolds Number) using Computational Fluid Dynamics (CFD). The methodology is validated using published literature, and the results of CFD are discussed for possible application in the estimation of glider turning motion.
Key Words
CFD; fuselage; glider; hull form; STAR CCM
Address
R.V. Shashank Shankar and R. Vijayakumar:Department of Ocean Engineering, IIT Madras, Guindy, Chennai 600036, India
Abstract
The global performance of a 15MW floating offshore wind turbine, a newly designed semi-submersible floating foundation with multiple heave plates by CNOOC, is investigated with two independent turbine-floater-mooring coupled dynamic analysis programs CHARM3D-FAST and OrcaFlex. The semisubmersible platform hosts IEA 15MW reference wind turbine modulated for VolturnUS-S and hybrid type (chain-wire-chain with clumps) 3x2 mooring lines targeting the water depth of 100m. The numerical free-decay simulation results are compared with physical experiments with 1:64 scaled model in 3D wave basin, from which appropriate drag coefficients for heave plates were estimated. The tuned numerical simulation tools were then used for the feasibility and global performance analysis of the FOWT considering the 50-yr-storm condition and maximum operational condition. The effect of tower flexibility was investigated by comparing tower-base fore-aft bending moment and nacelle translational accelerations. It is found that the tower-base bending moment and nacelle accelerations can be appreciably increased due to the tower flexibility.
Key Words
15MW semi-submersible floating foundation; flexible vs rigid tower; free-decay simulation/experiment; fully coupled dynamics simulation; heave damping plates
Address
Da Li, Cong Yi, Wei Gao, Chunhui Song, Shenglei Fu: CNOOC Ltd, No. 6 Taiyanggong South Avenue, Chaoyang District, Beijing 100028, China
Ikjae Lee and Moohyun Kim: Department of Ocean Engineering, Texas A&M University, College Station, Texas 77843, USA
Alex Ran and Tuanjie Liu: OffshoreTech, LLC 1400 Broadfield Blvd, Suite 625, Houston, TX 77084, USA
Abstract
The vertical distribution of suspended sediments in the mangrove-mud coast is complicated due to the characterization of cohesive sediment properties, and the influence of hydrodynamic factors. In this study, the time-evolution of suspended sediment concentration (SSC) in water depth is simulated by a one-dimensional model. The model applies in-situ data measured in October 2014 at the outer station in Cu Lao Dung coastal areas, Soc Trang, Vietnam. In the model, parameters which have influence on vertical distribution of SSC include the settling velocity Ws and the diffusion coefficient Kz. The settling velocity depends on the cohesive sediment properties, and the diffusion coefficient depends on the wave-current dynamics. The settling velocity is determined by the settling column experiment in the laboratory, which is a constant of 1.8 x 10-4 ms-1. Two hydrodynamic conditions are simulated including a strong current condition and a strong wave condition. Both simulations show that the SSC near the bottom is much higher than ones at the surface due to higher turbulence at the bottom. At the bottom layer, the SSC is strongly influenced by the current.
Key Words
a one-dimensional model; Cu Lao Dung (Soc Trang, Vietnam); diffusion coefficient; settling velocity; suspended sediment concentration
Address
ien H. Le Nguyen and Phuoc H. Vo Luong: Department of Oceanology, Meteorology and Hydrology, Faculty of Physics and Engineering Physics, University of Science, Ho Chi Minh City, Vietnam;
Vietnam National University, Ho Chi Minh City, Vietnam 227 Nguyen Van Cu Street, Ward 4, District 5, Ho Chi Minh City, Vietnam
