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

Abstract

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 axebow 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.

CFD Analysis into the Resistance of Trimaran with Longitudinal Sidehull Adjustments

“…). [13]. The longitudinal side hull positioning has a relatively significant difference in CT values.…”

“…The near-wall performance of the kappealing model may be employed without the possibility of causing inconsistencies to its free stream sensitivity, and it provides highly precise predictions of the start and magnitude of flow separation under undesirable pressure gradients [16]. The SST model has benefited greatly from the strength of the fundamental turbulence model, which is why the development of an accurate and dependable near-wall formulation of the Wilcox model has greatly aided its industrial application of turbulence, heat, and mass transport [17], This is further supported by Utama et al [13] comprehensive research of trimaran ships.…”

“…According to Utama et. al [13], the formula for calculating the non-interference trimaran resistance is as follows:…”

“…Despite the complexity of multi-hull total resistance components, interference effects may be observed experimentally. An IF measures the degree of interaction between the hulls of a multihull [13]. IF is formulated in Equation (7), as follows:…”

Experimental and Computational Fluid Dynamics Investigations into the Effect of Loading Condition on Resistance of Hard-Chine Semi Planning Crew Boat

“…The comparison of numerical and laboratory findings revealed a high degree of agreement between them. Furthermore, CFD applications are used in the evaluation of water flows regarding the effects on ships (Suastika et al, 2017;Utama et al, 2021a), they presented that the CFD calculations and model testing correlate quite well for overall ship resistance in calm water.…”