Computational fluid dynamics study on demihull interference and shallow water effects on resistance and wash wave of high-speed catamaran ferry using OpenFOAM

This study presents a comprehensive analysis of the hydrodynamic resistance components, trim, and sinkage characteristics of a high-speed catamaran ferry through computational fluid dynamics (CFD) simulations utilizing the OpenFOAM CFD tool. By systematically introducing each physical effect step by step, this study investigates how free-surface waves, dynamic motions, demihull interaction, and shallow water affect the vessel's hydrodynamic behavior across a range of speeds. OpenFOAM's snappyHexmesh utility is employed for meshing of computational domain, while simpleFoam and interFoam solvers are utilized for doublebody and free-surface Reynolds-averaged Navier–Stokes simulations, respectively. Experimental validation confirms the accuracy of the simulations for catamarans operating in deep waters. Key findings indicate that the demihull interaction's effect is dependent on the vessel speed, demonstrating both positive and negative effects. Furthermore, a reciprocal relationship between demihull interaction and shallow water effects is observed, with each effect amplifying the other. The pressure resistance exhibits a significant increase around critical speeds in shallow water, accompanied by reduced resistance at higher speeds than in deep water. This phenomenon is attributed by changes in wave patterns when approaching the critical speed and augmented dynamic lift, particularly at the stern after critical speed, leading to reduced overall sinkage and trim.