The oscillatory free water surface motion inside OWC chamber for wave energy conversion

This paper presents a simple 1-D modelling to describe the behavior of the oscillating water column device (OWC) used for wave energy conversion. We are interested in the free water surface motion inside the chamber, it is considered as a piston mass moving up and down due to the successive incident monochromatic waves. Two models are considered: the model without turbine (assuming the transformation is isentropic) and the model with Wells turbine. The method of Lagrange has been used to derive the differential equations of the water free surface motion. Then the Poincaré-Lindstedt method has been applied in order to solve analytically the differential equations. It has been found that the resulting motion equations are similar to those of a 2^nd order oscillatory system. For such equations: the resonance regime is of great interest during the solution procedure. In the present paper the natural frequency of an OWC system has been identified for maximal performance.