Hydrodynamics of an oscillating water column seawater pump Part I: theoretical aspects

A wave-driven seawater pump, composed of a resonant and an exhaust duct joi ned by a variable-volume air compression chamber, is studied. The time depe ndent form of Bernoulli's equation, adapted to incorporate losses due to fr iction, vortex formation at the mouths and radiation damping, describes the pump behaviour. A dimensional analysis of the pump equations shows that a proposed scale-model will perform similar to a full-scale seawater pump. Fl uid oscillations in the ducts perform similar to a damped, two-mass spring system, excited by the waves. A resonant condition can be maintained, for d ifferent wave frequencies, by varying the volume of air in the compression chamber. The dimensional analysis shows that the basic behaviour of the pum p is linear and that its performance can be significantly increased by opti mising the design of the duct mouths. Linear estimates of the resonant air chamber volume and flow rate through the pump are derived. (C) 2000 Elsevie r Science Ltd. All rights reserved.