The influence width of drifting ships

Both vertical and horizontal boundaries affect the hydrodynamics of a ship. The first is commonly referred to as shallow water, and the second as restricted water. The combination of both is named confined water. The distinction between open water and restricted water is governed by the distance towards the closest obstacle in horizontal direction and is defined by the so-called influence width yinfl. This distance was elaborated based on a comprehensive test program carried out in the confined towing tank at Flanders Hydraulics in 2007, with a small ship model, and was adopted by the International Towing Tank Conference (ITTC, 2017).In this article a new, extensive test program at the same facilities is presented, using a small scale model of the well-known benchmark vessel KVLCC2, including tests at different drift angles to elaborate the validity of the influence width definition for non-zero drift conditions. It is shown that the definition still stands for drifting ships, if the width is expressed with respect to the point of the ship that is closest to the obstacle. The observed coupling with the blockage of the ship model and hence a possible tank dependency, leaves room for further research.