Numerical analysis of a fixed-type oscillating water column with irregular waves

Numerical analysis of a fixed-type Oscillating Water Column (OWC) with irregular waves was performed in the time domain using a fully nonlinear numerical wave tank (NWT) technique. Irregular incident waves as a form of PM spectrum were applied to the OWC system and the time series of surface elevation inside the chamber was calculated. The NWT was based on potential theory, boundary element method with constant panels, and the mixed Eulerian-Lagrangian (MEL) approach. A specially devised free-surface boundary condition inside the OWC chamber was implemented to describe both the time-varying pneumatic pressure due to airflow through the nozzle outlet and the viscous energy loss induced by vertically oscillating water columns. The quadratic models for pneumatic pressure and viscous loss were applied to the free surface boundary conditions, and their numerical results were compared for various incident wave spectra. The equivalent pneumatic and viscous damping coefficients were calculated by the linearization of quadratic models. The numerical results with the equivalent coefficients were compared with those with the quadratic coefficients. Copyright 2012 by the International Society of Offshore and Polar Engineers (ISOPE).

Numerical analysis of a fixed-type oscillating water column with irregular waves Conference Paper