Numerical analysis of multiple-chamber OWCs efficiency using a fast PTO modelling approach in OpenFOAM

Abstract

A Numerical Wave Tank is developed within the OpenFOAM® environment to study a Triple-Chamber Oscillating Water Column using a fast PTO modelling technique. Three PTO modelling approaches are studied: the first physically represents the damping holes in the experiments, and two others use damping numerical regions; the second models the PTO as a porous media inducing momentum loss, and in the third, the PTO is modelled by a sink of momentum induced by a linear velocity damping term. The calibration and validation of the Numerical Wave Tank are done for a Dual-Chamber Oscillating Water Column using the three approaches. Approaches 2 and 3, which model the PTO as numerical regions, were faster, up to 40 %, compared to the real holes approach. Results show that including a third chamber in the Triple-Chamber has neglectable efficiency advantages for the lower damping PTO conditions. For the higher PTO damping conditions, the Triple-Chamber performs worse, having a primary efficiency of around 45 % compared to the 60 % from the Dual-Chamber. In this case, Approaches 2 and 3 were faster, up to 60 %, compared to the real holes approach in the Triple-Chamber case.