ABSTRACT:

The hydrodynamic behavior of a wave power absorbing caisson with lateral opening under the action of 2D linear wave is studied in this paper. To solve the potential flow field, a localized finite element method is adopted The pressure drop through the air nozzle is linearized by means of the principle of energy equivalency The theory is well conformed by model experiments

INTRODUCTION

In the study of wave energy utilization, a type of wave power converter called Oscillating Water Column Breakwater (OWCB) was presented by National Engineering Laboratory in Britain(Moody, 1982) and Port & Harbour Research Institute in Japan(OjIma,1983). To analyse the hydrodynamic behavior of owcb, Moody (1982) developed an equivalent floating body method and Ojima(1983) presented a thermodynamics and wavekinematics method In the first theory, the system is Simulated by an oscillating water column and a linear air damping In the second theory, the air turbine is replaced by an air nozzle, and thermodynamic equations are established to describe its performance, while the water elevation in the caisson is described by hydrodynamic equations. In this paper, a localized finite element method is adopted, namely, the potential flow in or adjacent to the caisson is approximated by finite element method and the potential function of the semi -infinite region is approximated eigenfunction expansion.

THEORETICAL ANALYSIS OF HYDRODYNAMIC BEHAVIOR

Fundamental Assumptions a Flow is perfect, incident wave is linear and normal, b Air flow in the air chamber and through air nozzle is an adiabatic and constant entropy process, and the compressibility of air is neglected; c The seabed is horizontal

2. Linearization of Pressure Drop through Air Nozzle

Under the action of wave, water surface in the caisson oscillates vertically, and air flow IS induced through the nozzle at the upper part of the air chamber.

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