The effects of closing angle and proximity of free surface on separation on a submerged body of revolution

Abstract

This thesis conducts an experimental investigation of the effects on separation of the closing angle of the stern section, the depth of submergence or proximity of the free surface, and the speed of a submerged body of revolution. The results of this investigation are then compared to the results obtained from two existing theoretical criteria for the prediction of the separation point on such bodies in turbulent flow. The point of separation is observed experimentally by photographing dye-flow patterns over the stern of the model at three speeds from .75 to 1.7 knots, at three depths of submergence corresponding to surfaced, near surface and fully submerged conditions for five different body stern shapes increasing in streamlining from a blunt hemisphere to a finely shaped almost pointed section. Equivalent body profiles to the outside of the turbulent boundary layer displacement thickness are computed and potential flow pressure- velocity distributions based upon the equivalent profiles are calculated and used in evaluating the separation criteria.