An evaluation of force estimation models for axisymmetric hull and sail configurations in translation at drift
University of New Brunswick
An evaluation of current in-plane and out-of-plane force and moment models was performed for a generic submarine model at drift. Computational solutions were developed for an axisymmetric hull and sail configuration at small to moderate drift angles, and the results were validated through comparison with experimental results. Existing research provides either qualitative explanations of the flow patterns created, or quantitative results for the overall forces and moments on the full submarine configuration. Using Computational Fluid Dynamics (CFD) fills a gap in the current literature by providing force and vorticity distributions on the body. The existing algorithm was found to adequately predict the in-plane sideforce and rolling moment coefficients at all drift angles, while the yawing moment coefficient is overestimated. The out-of-plane force and moment coefficients for downforce and pitching moment are accurately estimated for angles of drift at or below 10°. At higher angles, these coefficients are significantly over-predicted, mainly due to particular model assumptions. This study has found that the interference effects of the sail on the hull forces, the downforce ahead of the sail trailing edge, and the interaction of individual vortex structures have a significant effect on the total forces experienced by the submarine. By incorporating these results in the existing force model, the maneuverability of submarines with sails could be better predicted, contributing to the safe operation of these underwater vehicles.