Numerical Insights Into the Resistance Reduction Mechanisms of Forward Tapered Transoms in High-Speed Catamaran: A Computational Fluid Dynamics-Based Study

Abstract

This study investigates the hydrodynamic influence of forward transom tapering on a displacement catamaran hull using computational fluid dynamics (CFD) simulations. Five taper configurations ranging from a vertical transom base design to a fully tapered stern (1.00B) were evaluated over a wide Froude number range (Fr = .3 to 1.0). The simulations were performed using a RANS-based solver coupled with the volume of fluid (VOF) method to accurately capture free-surface effects. Turbulence was modeled using the SST k–ω approach to account for boundary layer evolution and wake separation. The analysis focused on resistance components, free-surface wave elevation mapping, transom pressure distribution, and wake streamline to assess hydrodynamic performance. Results indicate that forward tapering significantly affects pressure resistance while frictional resistance is slightly altered. The 0.75B taper configuration consistently demonstrated optimal performance, reducing the total resistance coefficient (C_T) by up to 6.39% and enhancing stern pressure recovery without introducing flow instabilities at higher speeds. Wave elevation analysis revealed a marked reduction in stern hollows and improved surface coherence with longer tapers. Transom pressure mapping showed attenuation of suction zones, while streamline visualizations illustrated wake narrowing and recirculation suppression in tapered configurations. The novelty of this study lies in its focus on geometric forward transom tapering. These findings not only advance the understanding of transom hydrodynamics but also establish the 0.75B forward taper configuration as a practical and efficient design recommendation for resistance reduction in high-speed displacement catamarans.

Keywords

catamaran resistance / CFD / RANS / transom forward taper / VOF

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2025 The Author(s). International Journal of Mechanical System Dynamics published by John Wiley & Sons Australia, Ltd on behalf of Nanjing University of Science and Technology.