A CFD-Based Parametric Study of Trimaran Form Factor and Resistance Characteristics

The form factor method is a semi-empirical approach commonly used to estimate the total resistance of a surface vessel. However, determining the form factor for trimarans with different outrigger layouts remains a challenging issue due to the complex hydrodynamic interactions involved. This study investigates the influence of the forward speed and the outrigger layout on the trimaran form factor, emphasizing their role in the total resistance prediction. A total of 30 scenarios are analyzed, covering six outrigger layouts and five speed conditions within the Froude number (Fr) range of 0.3 to 0.5. The total resistance is computed through Computational Fluid Dynamics (CFD) simulations using OpenFOAM. The numerical model is validated against experimental data. Simultaneously, potential flow theory is applied to estimate the wave-making resistance, enabling the derivation of the form factor values under various conditions. The results reveal that both outrigger layout and forward speed significantly influence the form factor, offering a practical and efficient framework for resistance estimation and outrigger layout optimization in early-stage trimaran design.