Effects of orifice size on the efficiency of a heaving oscillating water column

Abstract

Oscillating water columns (OWCs) have been studied extensively as promising wave energy converters. Different factors can affect the pneumatic power of OWCs, such as model scaling, turbine damping, and air compressibility. In this study, the heave motion of the OWC was limited by adding friction, and the effect of orifice size on the pneumatic power of an OWC from an unconstrained to a fixed position was investigated using a numerical method combining the k-ε/laminar model, the VOF interface capturing method, the motion-based zonal mesh update method and the 6DOF solver. Two groups of validation experiments and a study of model scaling were carried out to verify the effectiveness of the numerical method. It is concluded that the orifice open area ratio has an optimal value of approximately 1% whether the model is stationary or heaving; however, the heave motion has a significant weakening effect on the pneumatic power. More power can be extracted by constraining the heave motion of the OWC.

Keywords

• oscillating water column
• pneumatic power
• open area ratio
• heave motion
• model scaling