Barge motions in random seas – a comparison of theory and experiment

Abstract

This paper describes a comparison of experimental data and theoretical results for the motions in waves of large flat-bottomed barges having zero forward speed. The experimental data are derived from model tests at two scales (1:36 and 1:108). These consist of measurements of motions in surge, sway, heave, roll, pitch and yaw to long-crested seas approaching the barge models at two orientation angles (head and beam seas). The experimental data are compared with results computed from linearized potential-flow theory, which accounts for the diffraction and radiation of gravity waves around the barge. The boundary-integral scheme employed to solve this potential-flow problem is briefly reviewed.The experimental data at two scales and the theoretical results show that potential-flow theory is in reasonable agreement with experimental data for all motions except roll near resonance. These roll-motion discrepancies, due to vortex shedding from bilge-keel edges, are discussed. Some of the observable effects of scale in the model tests are highlighted.