Behavior of Hydrodynamic Force Acting on Lateral Motion Ships in Extreme Shallow Water

The behavior of hydrodynamic forces acting on a ship at lateral motion was investigated. Force measurement in towing tank and numerical simulation on viscous flow field were made, and correlations of hydrodynamic forces with flow field around ships were examined. A large flow pattern change at extreme shallow water case such as H/d<1.20 was observed in model scale, and it causes serious characteristics change of lateral force. Present characteristics change could be caused by the pre ssure loss at the gap between sea bottom and ship bottom, which may be referred by ‘retaining effect’, and that generates the upstream flow pattern and separation pattern change.