Free-Decay Heave Motion of a Spherical Buoy

We examined the heave motion of a spherical buoy during free-decay drop test. A comprehensive approach was adopted to study oscillations involving experimental measurements and complementary numerical simulations. The experiments were performed in wave tank equipped with an array high-speed motion-capture cameras set high-precision gauges. simulations included three sets calculations varying levels sophistication. Specifically, one set, volume-of-fluid (VOF) method used solve incompressible, two-phase, Navier–Stokes equations on overset grid, whereas other based Cummins mass-spring-damper models that are both rooted linear potential flow theory. Excellent agreements observed between data results VOF Although less accurate, predictions two reduced-order found be quite credible, too. Regarding buoy, obtained indicate that, after being released from height approximately equal its draft at static equilibrium (which is about 60% radius), underwent nearly harmonic damped oscillations. conducted analysis reveals length has profound effect frequency attenuation rate For example, compared same size half submerged (i.e., tested oscillated period roughly 20% shorter, amplitude decayed almost twice faster per period. Overall, presented provides additional insights into response floating sphere can for optimal design energy extraction.