Numerical investigation of offshore oscillating water column devices

The main objective of this paper is to analyse the hydrodynamic efficiency of offshore stationary OWC devices with different configurations through two-dimensional computational fluid dynamics simulations. The two-dimensional incompressible Reynolds-Averaged Navier-Stokes equations and the Shear Stress Transport (SST) k-ω turbulence model are solved for the simulation of water moetion under regular waves. The airflow through the turbine is calculated using a compressible aerodynamic model. After the numerical model is validated using the experimental data, it is used to analyse the effect of the submerged draught of rear vertical wall of the OWC on the hydrodynamic efficiency, and the improvement of hydrodynamic efficiency by a horizontal bottom plate attached to the back wall. The numerical results prove that increasing the rear wall draught improves the hydrodynamic efficiency if the front wall draught is 0.25 times water depth. If the draughts of the front and rear walls are the same, increasing them simultaneously causes a reduction in the hydrodynamic efficiency. Attaching a horizontal bottom plate on the deeper rear vertical wall improves efficiency. The best efficiency increases with the increase of the length of the bottom plate until the plate length is twice the chamber length. Further increase in the bottom plate length causes a reduction in the best efficiency.