Real-time coupled potential and viscous flow method for floating structures with heave plates

Heave plates are widely used to suppress the heave motion of floating structures by introducing substantial viscous damping and added-mass effects, both strongly dependent on the Keulegan–Carpenter number due to nonlinear vortex formation and shedding. While two-phase computational fluid dynamics (CFD) can accurately resolve these phenomena, its high computational cost limits routine engineering applications. Conversely, potential-flow methods augmented with Morison terms require empirical calibration of the drag coefficient (CD), reducing predictive robustness. This study presents a real-time coupled framework that integrates a global potential-flow solver for wave diffraction and radiation with a localized single-phase CFD solver to resolve the highly nonlinear flow around heave plates. The solvers share the same equations of motion and advance body dynamics through direct force coupling at each time step. Validation against published experiments and two-phase CFD benchmarks for heave-plated cylinders under free-decay, forced-oscillation, and regular-wave conditions demonstrates accurate prediction of amplitude-dependent damping, natural-period shifts, and resonance suppression. In free-decay simulations, the predicted natural periods agree with the two-phase CFD and experimental results within 3%, while the damping ratios deviate by less than 7%. The proposed framework reduces the computational cost by more than 25 times in terms of CPU-hours. Parametric studies over varying plate-diameter ratios and submergence depths reveal that increasing plate size amplifies nonlinear damping and added-mass effects, leading to prolonged natural periods and reduced resonant responses.