Hydrodynamics of Heaving Oscillating Water Columns in Low Keulegan-Carpenter Flow Regimes

Wave Energy Converters (WECs) supporting small blue-economy sensor-type applications operate in a flow regime characterized by low Keulegan-Carpenter (KC) number. Inviscid linear potential flow models have demonstrated performance supporting design of Wave Energy Converters, though accuracy is challenged at low KC where non-linear viscous drag is a proportionally larger factor. This study explores the dependency of viscous drag on geometric features on small Oscillating Water Column (OWC) type WECs by empirically fitting potential flow theory based numerical models using experimental data. Three geometric variants are considered with differences in sharp-edges across a range of resonant and non-resonant regular wave forcing frequencies. Confirming previous theories, sharp-edges play a disproportionately large role in viscous drag in low KC flow regimes. These results promote an improved understanding of non-linear viscous drag supporting the design and development of small WECs for the blue-economy.