Numerical Study on Form Factor Determination for Trimarans With Different Outrigger Layouts

Abstract The (1+K) method has been widely applied in ship resistance calculations. However, determining the form factor for more structurally complex trimaran configurations remains a subject of debate. This study investigates the calculation method of the form factor (1+K) for determining total resistance of trimarans and examines its variation patterns in relation to the forward speed and outrigger layout. This study investigated a total of 15 scenarios, including 3 outrigger layouts and 5 forward speeds. Computational Fluid Dynamics (CFD) method based on the OpenFOAM is utilized to calculate the total resistance of trimarans across a range of outrigger layouts and forward speeds. The numerical simulation results were compared with experimental data, validating the efficient and accuracy of the numerical simulations. Simultaneously, potential flow theory is applied to determine the wave-making resistance of the trimaran and further derive the form factor under these scenarios. Through this approach, the variation of the form factor with changes in speed and outrigger layout is systematically analyzed. Results demonstrate the variation trends of the total resistance of the trimaran with respect to the longitudinal distance (a), transverse distance (p), and forward speed. Revealing how both speed and outrigger layout significantly influence the form factor, providing more efficient method for trimaran design in terms of resistance.