Flow Around Ships at a Small Angle of Yaw and Their Hydrodynamic Forces

Abstract

Flow around model ships of a container carrier and a tanker with a small angle of yaw are observed by the dye tracer method and the vorticity distributions at some sections are also measured. From the observed results, the vorticities in the lee side of the aft body are allowed to roll up and form a concentrated vortex and the vorticities from the bow bilges of the tanker flow down and along the bottom. The flow around ships are calculated by the invisid strip method with a number of vortex-lines which are emanated from the separation points at each section and extend down stream along a stream line. The calculated vortex positions are compared with the observed results. The calculated side force distributions and hydrodynamic forces acting on a ship are also compared with the measured ones and it is concluded that the leading and trailing edge effects must be taken into account to calculate the side force distributions and hydrodynamic forces by the strip method.