Dorothy is a 3D unsteady Langrangian Vortex code dedicated to the simulation of tidal turbines taking into account more and more real features of the marine flow. This software is the result of a collaboration between University Le Havre Normandy and Ifremer. It is used in many of our National and/or International research projects for local or global characterisation of turbine(s) behaviour.

Dorothy is based on the Vortex method, where the flow is discretised using vorticity carrying particles and the turbines are represented using a panel method. The name “DoROThy” was initially chosen because of the “ROT” letters that symbolise “rotational”, another word for vorticity. Therefore, in this numerical method, the Navier-Stokes equations for an unsteady and incompressible flow are used in their velocity/vorticity formulation.

To be more precise, the velocity is obtained using the Biot & Savart relation. By means of a viscous splitting, diffusion is handled via a Particle Strength Exchange model. Additionally, an LES model with a turbulent eddy viscosity completes the numerical model for diffusion. Turbulent inflow conditions are generated by a Synthetic-Eddy-Method for a given turbulence intensity and a given anisotropic ratio.

The code is broken down into several modules dealing with different features of the computations: turbine wakes, ambient turbulence, turbine interaction. Future developments (under progress) will improve the performance assessment, structural loads and flow perturbations. Further improvements are considered such as the account of wave, better LES turbulent model, fluid-structure interaction.