A Contribution to Flow-Separation Problems in Unsteady Motion of a Body

Abstract

Roll motion is the least predictable of ship motions, largely because of viscosity effects, which in turn causes flow separations to occur. As a result of these phenomena, roll damping is often highly nonlinear. It is best estimated in the present state of the art by strictly empirical methods. &&In this report, several relevant flow-separation problems are studied from a fundamental point of view. These are divided generally into two categories: (i) boundary_layer separation and (ii) sharp_edge separation. In both cases, starting motion and oscillatory motion are considered separately. Emphasis is placed on rather simple methods of calculations. Results are compared with experiments and/or more detailed calculation methods wherever such are available. Finally, a procedure is proposed (but not carried out) for treating the formation of vortex sheets by a translating rolling ship hull.