Development of Advanced Turbulence Model for Prediction of Ship Stern Flow

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The recent advancement of computational fluid dynamics has enabled further application of the technique to ship hydrodynamics. However, turbulence model has still been one of the most important issues for accurate prediction of ship stem flow, where strong longitudinal vortices are normally involved. The objective of the present research project is to develop new turbulence model to overcome the problem. Three years had been used to complete the present work.In the first year, main focus was placed on investigation on basic concept and strategy to modify the conventional k-ε turbulence model. Initial validation of the new model was done in application to relatively simple flow filed, i.e., longitudinal vortex flow in flat plate boundary layer. Detailed comparison of the numerical results with experimental data indicated that the present model clearly improved resolution of the mean-velocity field, although that of Reynolds stress fields was somewhat unsatisfactory.In the second and third years, the new turbulence model had been applied to ship flow computation, in conjunction with further modification of the model associated with introduction of nonlinear eddy viscosity expression, which had, in conclusion, appeared to be capable for more accurate prediction of Reynolds stress fields. Furthermore, in the final year, application of the present model had been extend to internal flow, i.e., circulatory turbulent flow in a straight pipe. Through the above-mentioned evaluations, the present turbulence had been shown to offer evident advantage over the conventional k-ε model, and that leads to an important conclusion that original goal of the present research project had been achieved with satisfactory accomplishments.