Experimental Study on Reynolds Number Effects in Propeller Open-water Test Using a Large Cavitation Tunnel

This study investigated the effects of Reynolds number (Rn) on Propeller Open-Water (POW) test results for the KP458 propeller (P/D = 0.7) using the Hanwha Ocean Cavitation Tunnel (HOCT). Tests were conducted under five Reynolds number conditions ranging from 0.35×10⁶ to 1.25×10⁶ while maintaining turbulence intensity at 0.8~1.1%. For selected Reynolds numbers (0.35×10⁶, 0.51×10⁶, and 0.77×10⁶), the results were cross-validated with measurements obtained in the Hanwha Ocean Towing Tank (HOTT). The results showed that propeller efficiency increased with Reynolds number up to 1.00×10⁶, with maximum efficiency occurring at an advance ratio of J = 0.60~0.65. The thrust coefficient (KT) approached a saturation region at Rn = 0.51×10⁶ ~0.77×10⁶, while the torque coefficient (KQ) exhibited reduced Reynolds number sensitivity beyond Rn = 0.51×10⁶. At the highest Reynolds number (1.25×10⁶), sheet and face cavitation developed over the entire advance ratio range, causing a reduction in efficiency due to thrust loss. The results at Rn = 1.00×10⁶ were extrapolated to full-scale conditions using the ITTC-78 method. The trends of KT, KQ, efficiency, and the optimum advance ratio were preserved, indicating that sufficiently high-Reynolds-number cavitation tunnel tests can provide reliable full-scale performance predictions.