Experimental and Numerical Investigation into the Effect of the Axe-Bow on the Drag Reduction of a Trimaran Configuration

Using the axe-bow to reduce total ship resistance on monohull ships has been well-known. This advantage has been further applied to a trimaran configuration together with its space-to-length (S/L) ratio differences. The investigation was carried out experimentally using an ITTC standard towing tank and numerically using computational fluid dynamics (CFD) analysis. The base model for the study uses an NPL 4a both for the mainhull and sidehulls of the trimaran, and later the mainhull is modified by attaching a front bulb known as an axe-bow. The resistance analysis of the trimaran was conducted with and without an axe-bow on the mainhull together with S/L ratios of S/L = 0.3 and S/L = 0.4 and at various Froude (Fr) numbers: 0.15, 0.2, 0.25, 0.3, 0.4, and 0.5. The results showed that the monohull with an axe-bow had a smaller drag than that without an axe-bow of an order up to 11.5%, whereas in the trimaran form, the reduction of drag was up to 8.4%. This indicates a positive influence of using the axe-bow on the total resistance of the trimaran configuration. Both experimental and CFD methods showed positive agreement of the order 2.7% discrepancy for the monohull form and a 3.4% discrepancy for the trimaran configuration.