Numerical Analysis of the Influence of Geometry on a Large Scale Onshore Oscillating Water Column Device with Associated Seabed Ramp

Abstract

The current study aims to perform a geometrical investigation of an onshore Oscillating Water Column (OWC) on a large scale. The Constructal Design method is employed, aiming to maximize its available power. The OWC is subjected to two constraints (areas of the chamber and ramp below the chamber); and three degrees of freedom: height/length ratio of the chamber (H1/L1), height/length ratio of the ramp (H2/L2), and submersion of the frontal wall of the chamber (H3). A laminar, unsteady, incompressible, and two-phase flow was adopted, solving conservation equations of mass, momentum, and transport of water-air volume fraction using Finite Volume Method (FVM) and Volume of Fluid (VOF) model. The global optimal geometry led to a twice maximized available power 37.3% higher than the best case without the seabed ramp below the chamber and seven times better than the worst case. Concerning the sensibility of geometry, results indicated that the chamber geometry, given by ratio H1/L1, over the available power (P) was strongly affected by the ramp ratio H2/L2. Moreover, the behavior of the effect of H2/L2 over the once maximized available power (Pm) and corresponding optimal shape of the chamber, (H1/L1)o, changed dramatically for two different magnitudes of H3 investigated.