The paper presents a numerical study of the air-flow in a typical pneumatic chamber geometry of an oscillating water column (OWC) type wave energy converter (WEC), equipped with two vertical-axis air turbines, asymmetrically placed on the top of the chamber. Outwards and inwards air-flow calculations were performed to investigate the flow distribution at the turbine inlet section, as well as the properties of the air-jet impinging on the water free-surface. The numerical study was performed using the FLUENT code. Steady and periodic flow conditions were assumed in the calculations.
The original design of the OWC is likely to be harmful for the operation of the turbines due to the possible air-jet-produced water-spray at the water free-surface subsequently ingested by the turbine. A geometry modification of the air chamber, using a horizontal baffle-plate to deflect the air from the turbines, is proposed to reduce the risk of water-spray production from the inwards flow. The influence of three different baffle-plate geometries was studied and two of them proved to be very effective. The flow distribution at the turbine inlet section for the outwards flow was found to be fairly uniform for the geometries considered, providing good inlet flow conditions for the turbines. Steady flow was found to be an acceptable model to study the air-flow inside the pneumatic chamber of an OWC-WEC.