Constructal Design Applied to the Geometric Evaluation of an Oscillating Water Column Wave Energy Converter Considering Different Real Scale Wave Periods

Abstract

The present work presents numerical study of the influence of geometry on the performance of an oscillating water column (OWC) wave energy converter by means of a constructal design. The main purpose is to maximize the root mean square hydrodynamic power of device, (P_hyd)_RMS, subject to several real scale waves with different periods. The problem has two constraints: hydropneumatic chamber volume (V_HC) and total OWC volume (V_T), and two degrees of freedom: H₁/L (ratio of height to length of the hydropneumatic chamber) and H₃ (OWC submergence). For the numerical solution it was used a computational fluid dynamic (CFD) code, based on the finite volume method (FVM). The multiphasic volume of fluid (VOF) model is applied to tackle with the water–air interaction. The results led to important theoretical recommendations about the design of OWC device. For instance, the best shape for OWC chamber, which maximizes the (P_hyd)_RMS, was achieved when the ratio (H₁/L) was four times higher than the ratio of height to length of incident wave (H/λ), (H₁/L)_o = 4(H/λ). Moreover, the optimal submergence (H₃) was achieved as a function of wave height (H) and water depth (h), more precisely given by the following relation: h − (3H/4) ≤ (H₃)_o ≤ h.