Air-water two-phase flow modelling of hydrodynamic performance of an oscillating water column device

A numerical method based on a two-phase level set with the global mass correction and immersed boundary method is developed here to simulate wave interaction with a semi-submerged chamber. An oscillating water column, where power is extracted due to a normally incident wave forcing the free surface of the fluid between the front wall and rear wall to oscillate, is studied numerically to examine its hydrodynamic characteristics. The numerical results for an OWC under various wave conditions are compared with published experimental data by Morris-Thomas et al. [Morris-Thomas TM, Irvin RJ, Thiagarajan KP. An investigation into the hydrodynamic efficiency of an oscillating water column. J Offshore Mech Arct Eng 2007;129:273–8] and theory by Evans and Porter [Evans DV, Porter R. Hydrodynamic characteristics of an oscillating water column device. Appl Ocean Res 1995;17:155–64]. The flow field, free surface and pressure distribution are presented at different instants in time to reveal the energy loss clearly. The hydrodynamic efficiency predicted by the numerical results demonstrates a banded efficiency centred about a resonant peak and agrees with the physical experiment more closely than with the inviscid linear theory. The effect of the various wave conditions, immersion depth, thickness of the front wall of the chamber, vortex generation around the front wall in the water and air chamber characteristics on the efficiency of wave energy extraction from the OWC is investigated.