A Numerical Study on Hydrodynamic Performance and Propeller Design for Small Coastal Craft

Small coastal crafts are often equipped with stock propellers selected from limited commercial options, without detailed matching among the hull, main engine, reduction gear, and propeller. This study presents a practical and integrated procedure for evaluating propulsion performance and designing a propeller tailored to a G/T 4.99 coastal craft under the fully loaded departure condition. The CFD resistance simulations were validated against model test measurements of resistance, sinkage, and trim and were applied over a wide range of vessel speeds. Self-propulsion simulations were subsequently conducted to evaluate the propulsive characteristics of the target vessel. Based on the evaluated self-propulsion characteristics, actual engine specifications and propeller installation data from Korean coastal vessels were used to select the main engine and reduction gear and to define practical ranges for the propeller diameter and pitch ratio. An initial propeller was determined using the Bp−δ method, after which the mean pitch ratio was iteratively corrected through full-scale performance prediction. The final propeller was selected by matching the predicted rotational speed under the trial condition to the target value determined by the engine and reduction gear while confirming the attainable vessel speed under the service condition with a 15% sea margin. The final propeller was evaluated through CFD self-propulsion simulations and compared with the stock propeller. At 16 and 18 knots, the designed propeller increased the overall propulsive efficiency by 8.4% and 10.1%, respectively, while reducing the required delivered power by 7.8% and 9.2%. These results demonstrate that the proposed procedure can improve the matching among the hull, machinery, and propeller and provide a practical basis for designing efficient propellers for small coastal crafts.