Study on Computational Method of Predicting Ship Viscous Flow

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The final goal of the present research is to clarify the nature of the viscous flow fields around a ship hull associated with complicated three-dimensional flow separation, by applying some methods of computational fluid dynamics. For this purpose the present project has aimed to develop computational schemes, to carry out measurements of flow and forces, and then to clarify the ship viscous flow by use of the computational methods.In the first year discussions were made on the validity of existing numerical schemes of solving Napier-Stokes equation, discretization methods, computational grids, and methods of solving pressure equation, in order to obtain reasonable methods.The second year, i. e., the final year is devoted to make trial computations on several flow problems for examining the validity of the methods developed. The first trial is an application of the methods to compute an optimal body shape with minimum viscous resistance in two-dimensional plane. The scheme is associated with an nonlinear programming technique. The body shape solved has a lens shape with sharp corners at both ends. The next case is applied to a problem of current flow in Osaka Bay, by which an large scale vortex motion near Akashi channel is simulated. The final trial computation is applied to the flow around a circular cylinder with varying diameter in chord direction. A typical three-dimensional pattern of unsteady flow separation is obtained showing a similar nature to the flow around ship hull.Measurements of hydrodynamic forces are also made in the second year, in which an analysis of measurement uncertainty is applied to the resistance test of a ship model.Although these results are not directly related to the ship viscous flow, it is certain that they offer firm basis of treating the fundamental mechanism of the viscous flow around ship hull in near future.