Experimental study of the drift of floating disks in regular waves

• Parametrization of drift speed of a floating disk depending on three dimensionless parameters characterizing the shape of the disk and the properties of a regular wave. • Formulation of a mathematical model describing the wave drift of floating disks simulating bergy bits and floes. • Calculation of the drag coefficient for wave drift of a floating disk. • Field measurements of three-dimensional accelerations with IMU buoys deployed on a bergy bit in the Barents Sea. Small icebergs, bergy bits and fragments of consolidated ice ridges can gain significant kinetic energy and pose a significant impact threat for ships and offshore installations in the Barents Sea. An experimental study of the response of floating disks simulating bergy bits to regular waves was conducted in the wave flume of the University of Oslo. The geometric scale factor, which determines the ratios of the disk sizes and wavelengths at full and laboratory scales, was equal to 400. The study focused on the mean drift and surge motion of the disks. Based on the results of 50 tests, the dependencies of normalized mean drift velocities and surge amplitudes on three dimensionless parameters expressed via the diameters and heights of the disks, the wave amplitudes and wavelengths were approximated. Based on the experimental data, it has been found that regular swell with an amplitude of 1 m may influence the drift of bergy bits with an average velocity of about 40 cm/s. The amplitudes of surge and heave oscillations of bergy bits turned out to be similar to the amplitudes of the swell. The latter was confirmed by data obtained from a buoy equipped with an inertial measurement unit (IMU) installed on a bergy bit in the Barents Sea in 2019. A model of bergy bit drift under regular waves was formulated, based on the balance of wave drift forces, wave damping force, and form drag force. The form drag coefficient has been calculated depending on the product of the disk diameter and the wave number according to the model with using the experimental data.