Practical estimation of sinkage and trim for common generic monohull ships

Abstract

Two practical approaches for estimating the sinkage and the trim experienced by a freely floating ship that advances at a constant speed in calm water are considered for common monohull ships at moderate Froude numbers F≤0.45: an experimental approach based on experimental data, given in the literature, for 22 ship models; and a numerical approach based on a practical linear potential-flow theory, the Neumann-Michell theory, that only requires simple flow computations. The experimental approach yields particularly simple analytical relations for the sinkage and the trim, and thus requires no flow computations. The numerical approach only involves flow computations for the ship hull in equilibrium position at rest; i.e., sinkage and trim effects on the position of the ship hull are ignored in these flow computations. Both approaches are found to yield reasonable predictions of sinkage and trim for a wide range of monohull ships at Froude numbers F≤0.45.