Sajad Hajizade

The hydrodynamic performance of high-speed planing vessels is significantly affected by hull geometry, especially the longitudinal variation of deadrise. Conventionally, positive deadrise angles, V-shaped sections, are adapted to reduce slamming loads, whereas recent studies have shown that negative deadrise, inverted V-shaped sections, can enhance lift and change the pressure distribution. Despite these findings, the hydrodynamic behavior of hybrid hull configurations, combining negative and positive deadrise angles, is not sufficiently understood. This study addresses this gap through a systematic CFD-based comparison of constant negative, constant positive, and hybrid variable-deadrise hulls using RANS simulations in OpenFOAM. After a grid convergence assessment and validation against available experimental data, results show that constant negative deadrise hulls generate higher lift and higher drag than constant positive ones, while hybrid configurations exhibit distinct behavior. Findings reveal that the hydrodynamic performance of a hybrid hull does not simply divide or interpolate between negative and positive angles. Hybrid configurations with short negative-deadrise sterns yield the highest levels of lift and drag, whereas extending the negative region reduces these forces. Analysis of the lift-to-drag ratio further shows that a hybrid transitioning from −20◦ to +20◦ provides the most robust performance, maintaining a high ratio across the examined range of hybrid configurations.