Lineår modelling of oscillating water columns including viscous loss

Abstract Wave-energy converters of the oscillating-water-column (OWC) type with pneumatic power take-off may be modelled by the so-called ‘applied-pressure’ (or ‘pressuredistribution’) description. For wavelengths which are not too short, the alternative ‘rigid-pistoa’ description is also applicable. The paper presents a transformation between the two descriptions. A mechanical mass-spring equivalent model of the OWC is also presented together with analog electric circuit diagrams. Some account of viscous energy loss is taken into consideration by introducing a mechanical loss resistance into the rigid-body description, and corresponding analog electric circuit elements for both descriptions are included. Some methods are presented to determine experimentally the mechanical loss resistance for a two-dimensional OWC.