Influence of liquid surface movement in chamber on conversion characteristics of offshore OWC device under irregular waves

The movement pattern of the liquid surface in the chamber is closely related to influence mechanism of structural parameters on the efficiency of the OWC (Oscillating Water Column) device. However, the morphology of liquid surface is difficult to quantify under the action of irregular waves, which hinders in-depth research on the energy capture mechanism. Regarding this issue, based on the physical test, the chamber liquid surface coefficient Cη is proposed, the effects of structural parameters (PTO (Power Take Off) coefficient α, chamber length Bs, internal depth Jn, and under water length of front wall Je) and wave parameters on the liquid surface in the chamber were discussed. The influence mechanism of structural parameters on hydrodynamic characteristics is revealed from the perspective of liquid surface movement. The main conclusions are as follows: The proposed coefficient Cη can reflect the difference between real liquid surface and the uniform oscillating water column. The smaller the Cη, the liquid surface in chamber is closer to the uniform column. The method using the liquid data at the center of chamber instead of the average data could bring unstable error (up to 2–3 times). Changing structural parameters affects the movement pattern of liquid surface within chamber, altering the proportion of energy cannot be captured due to the irregular deformation. This could be part of the mechanism by which parameters affect the hydrodynamic characteristics. The results can provide a reference for the improvement of research methods for OWC devices.