Theoretical approach to the scale effects of an OWC device

Abstract

This research deals with the dynamic similarity problem for Oscillating Water Column (OWC) devices, for which air is the fluid that is subject to thermodynamic transformations in the inhalation/exhalation phases. Based on the differential problem, both linearized and full-nonlinear, the scale ratios satisfying similarity are calculated, with specific reference to the case where constraints are present on some of these scale ratios. The paper proceeds to identify the numerous processes of a turbulent interface that scales differently between model and prototype. With the aim of bringing to front the influence of the scale effects on featured aspects of the thermodynamic process involved, it is proposed that a non-equilibrium thermodynamics approach can be more comprehensive and representative not only of transformations, but also of scaling. The study reveals that in the case of OWC thermodynamics, non-equilibrium states which would be less evident in scaled model, would become more relevant as the scale is increased towards the size of the prototype, with consequences on performance.