A Simplified Model for the Interaction Between the Boundary Layer and Longitudinal Vortices (3rd Report) : Interaction Between the Plate Surface and Longitudinal Vortices

Abstract

The behavior of the bilge vortices in the stern flow field of full ship forms is characterized by the interaction between the vortices and the hull surface, which yields the distorsion of wake distribution, too. This paper presents a study of the interaction between the boundary layer of the flat plate surface set in parallel to uniform flow and a longitudinal vortex generated by a wing tip inserted in the boundary layer. Numerical calculations are carried out and compared with experiments. It is shown that the inverse vortices are generated on the plate surface and are diffused and convected from the surface. The longitudinal vortex is forced out from the surface by the induced flow field of the inverse vortices. Scale effect of the flow field is also considered. It becomes clear that there seems to be a large scale effect about the position of the longitudinal vortex center, not only in y-coordinate but also in z-coordinate. Owing to this, the contraction rate of velocity distribution of main flow from model to ship is slightly smaller than the ratio of their frictional resistance coefficients.