Experimental and numerical investigation of the hydrodynamic performance of an oscillating water column wave energy converter

The performance of an oscillating water column wave energy converter is investigated based on both numerical and experimental approaches. The viscosity effects are neglected in the numerical approach and the boundary integral equation method (BIEM) is implemented to solve the appropriate 2D boundary value problem (BVP). The influence of turbine damping and wave period is evaluated in the numerical model in both regular and random waves. A comprehensive experimental campaign is carried out in both regular and irregular waves to validate the numerical results as well as to investigate the influence of wave height, period and turbine damping on the efficiency of the converter. High and low turbine damping conditions are imposed to the experimental model. It is found that both the numerical and experimental results have a satisfactory agreement for the small wave amplitudes. It is detected that the efficiency of the device is very sensitive to the variations in the turbine damping although the absolute maximum efficiency is less sensitive to the slight alterations applied to the turbine damping. It is observed in the experimental study that the influence of the wave height has less importance than the other two parameters (turbine damping and incoming wave period) although the effect of the wave height becomes prominent in high wave amplitudes and causes the efficiency of the device to become less sensitive to variations in wave period and to tend to have an uniform value in wide wave period ranges.The work has been conducted within the Strategic Research Plan of the Centre for Marine Technology and Ocean Engineering, which is financed by Portuguese Foundation for Science and Technology. The first author has been funded by the Portuguese Foundation for Science and Technology (Fundação para a Ciência e Tecnologia – FCT) under contract SFRH/BD/98287/2013. The experimental part of the work was conducted in the wave flume of the Hydraulics Laboratory integrated in the Group of Civil Engineering and Marine Energies (GICEMA), Escuela Politécnica Superior based on the scientific cooperation agreement between Instituto Superior Técnico and University of Santiago de Compostela.S

Numerical study of a novel ventilation system added to the structure of a catamaran for different slamming conditions using OpenFOAM

Large-size catamarans' structural behavior is sensitive and critical during the slamming phenomenon. “Ventilation pipes” within the center bow structure are proposed to discharge these cumulative pressure and related loads. The validation case is comprising two different simulation schemes, static and dynamic wedge. First, the appropriate method is chosen based on the accuracy and needed computational running time criteria. The numerical solution approach solves the RANS equation using the Open Field Operation and Manipulation (OpenFOAM) library called “InterFoam and OverInterDyMFoam for static and dynamic mesh respectively. Totally three different impact conditions with four different impact velocities (12 case studies) were considered for the case with added ventilation pipes (amended hull) and the standard model (parent-hull). Apart from the limitation of the proposed plan which is discussed, the results indicate that the recorded pressure and total force decreases by about (15%–50%), and (5%–25%) respectively