An advanced physical-mathematical model of ship-hull hydrodynamic forces deduced from simplified vortex model during manoeuvring motion in slow speed

One of the authors presented a conventional component-type mathematical model at MARSIM'93 and showed good agreement with experimental results of hydrodynamic forces acting on a hull in oblique and turning motion in slow speed. The main assumption in the model was that the viscous lift and induced drag are distributed concentratedly at both the fore and aft ends of the hull, The hydrodynamic coefficient, however, concerning the induced drag in the model in oblique motion was not useful in estimating the coefficient in turning motion. In this paper, we present a modified mathematical model similar to the conventional model, which is deduced from simplified vortex model. Furthermore, we discuss characteristics of the present model and differences between the conventional and present ones regarding induced drag. The present model can estimate rotative coefficients and hydrodynamic forces in turning motion by analyzed results of experiments in oblique motion, and the estimated results agree well with experimental ones of turning motion including the induced drag component.