Calculation of Flow with Three-Dimensional Separation Vorticities around Ships

Abstract

An invisid flow model based on the approximations of slender body theory is developed to calculate the flow with three-dimensional separation vorticities around ships at a small angle of attack. The vortex sheet can be represented by a number of free vortex-lines when it flow out from the thin boundary layer over the hull. Following the concept of this method, the two separation lines are defined from the pressure gradients on each side of the hull. Semi-infinite vortex-lines are emanated from the separation points at each section and extend downstream along a stream line. The force acting on a ship is analysed with the further development of the Newman's method and the new term of the force acting on the vortex-lines is found. The flow and the positions of the extended vortex-lines are calculated with a container ship and a tanker. From the calculated results, the followings are observed: 1) The vortex-lines emanated from the both sides of the tanker's bow flow down to the bottom but the vortex-lines near the bow of the container ship flow out far from the hull. 2) The vortex-lines are roll up near the lee side of the aft body. 3) Attachments of the vortex-lines emanated from the weather side of the mid-body are found.