A new method to simulate laminar-turbulent transition has been used to study flow around sailing yacht appendages. Based on an empirical correlation, the method allows to predict transitional flow in a fully 3Denvironment using unstructured grids and massive parallelization. Reynolds number of the flow around the appendages of sailing yachts is of an order where transitional flow plays an important role. The method thus serves as a highly valuable tool for realistic optimisation of yacht appendages.

The paper describes briefly Menters γ-ReΘtransition-model and shows its validity for the given purpose. 2D-analysis of NACA-profiles has been chosen to validate the transition model. The resulting lift and drag coefficients from the RANSE calculations have been compared with experimental data and results from the 2Dboundary layer code XFoil, showing reasonable agreement. The method then has been used for a bulb length optimisation of an appendage configuration of an ORC GP42 level racer. Here the differences between a fully turbulent and a laminar turbulent optimisation are shown and discussed.

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