Response of small sea ice floes in regular waves: A comparison of numerical and experimental results

In severe seas ice floes can gain significant kinetic energy presenting a hazard to offshore structures and shipping. A numerical investigation is presented to investigate the kinematic response of sea ice floes in waves. The results are compared against available experimental data. The surge, heave and drift velocity are analyzed for various different ice floe shapes using the potential flow model HydroSTA (R) and the viscous flow CFD model OpenFOAM (R). The results show relative wavelength (A normalized with floe length L-c) lambda/L-c strongly influences heave and surge, with a heave resonance occurring at lambda/L-c=8 for the cubic floe not being correspondingly observed for the square floe. The heave Response Amplitude Operator (RAO) is found to increase with floe thickness with a resonance occurring when relative thickness b/L-c >= 0.5. Shape is observed to be less important than thickness. At small values of lambda/L-c the floe is observed to move forward over the whole wavelength resulting in its drift displacement. Both vertical velocity relative to theoretical particle velocity V-y/V-p and ratio of forward and backward velocities show resonance at lambda/L-c=8. Comparing with experimental data, the linear analysis using HydroSTAR (R). overestimates the heave and surge RAOs. OpenFOAM (R), however, appears to provide a much better agreement with the experimental data indicating viscosity plays an important role in floe kinematics.