Analysis of slamming phenomena on a model of a cargo ship in irregular waves

Article type: Research Article

Authors: Ferdinande, V.

Affiliations: Laboratory of Naval Architecture, University of Ghent, Belgium

Abstract: Model tests in irregular head waves were analyzed with special emphasis on the slamming phenomena, endured by a cargo ship in the ballast condition. The conditions leading to slamming, i.e. the magnitude of vertical relative motions and relative velocities at the forward perpendicular, were evaluated. By means of theoretical computations of pitching and heaving motions and their phase angles in regular waves, relative motions and relative velocities could be evaluated at any station aft of the forward perpendicular. A distribution of the slamming decelerations, measured at a certain station near the bow, allowed one to determine the so-called “threshold velocity”, figuring in the well-known probability formula, which lets one predict the occurrence of slamming. These “threshold velocities” are calculated for different stations along the ship length and for different levels of slamming severity. It is noticed that these “threshold velocities” are dependent on ship speed. The meaning of the conception “threshold velocity” is discussed. In order to predict slamming, as recognized on a ship in bad weather, an indication concerning accepted slamming severities is given. Estimating the number of slams in a hundred motion oscillations which is likely to be accepted by a ship’s master, the attainable speed in the here investigated sea state is determined.

DOI: 10.3233/ISP-1968-1517101

Journal: International Shipbuilding Progress, vol. 15, no. 171, pp. 373-387, 1968