Assessing Dynamic Viscosity Effects on the Efficiency of Oscillating Water Columns

Oscillating Water Column (OWC) devices are among the most mature concepts for wave energy conversion. Nevertheless, their hydrodynamic performance remains strongly influenced by viscous and turbulent flow processes that are not yet fully understood. In particular, dynamic viscosity affects internal flow structures, pressure evolution, and energy dissipation within the OWC chamber, especially under nonlinear and energetic wave conditions. While classic wave theories have been widely employed to describe wave kinematics, their applicability becomes limited when localized viscosity effects and complex flow interactions govern the device behavior. To better understand the characteristics of these effects, the present study examines the role of dynamic viscosity in shaping the internal flow dynamics of an OWC using a combined experimental and numerical framework. Laboratory wave flume experiments conducted on a scaled cylindrical OWC model are complemented by numerical simulations based on the Navier–Stokes equations, with analytical solutions from Stokes’ fifth order wave theory used as a reference. The analysis focuses on relative hydrodynamic trends rather than absolute performance metrics, emphasizing pressure response, flow uniformity, and spatial variations of the inverse Reynolds number (1/Re) as indicators of viscous influence. Through systematic comparison between experimental observations, numerical predictions, and analytical solution, this study aims to assess how viscosity modifies internal OWC dynamics and to provide insight to the performance of OWC systems and their future development.