The current research aims to numerically predict the performance characteristics of the Oryon Water Mill. The simulation mechanism to be developed, begins at the structural solver part of a partitioned FSI solver, upon which the unique functional characteristics of the turbine are embedded. The modelling is carried out to account for the turbine’s functional characteristics like, multiple nested rigid body FSI dynamics, non-smooth dynamics and lamella partial torque contributions. The solver is built to resolve the turbine dynamics in two dimensions and re-scale the final result with respect to the turbine core height. The results of the simulation show the predicted torque to be of similar trend as that of the experimental data collected by MARIN, while being an over-prediction by a factor of two. The optimal performance range of the turbine is predicted within an error bound of 0.1RPS. The overprediction of the torque is considered to be a result of the 2D solution not accounting for the flow leakage in the third and unaccounted for direction. The time variant fluid solution is found to be unstable due to the spikes observed in the torque time signal and is a consequence of the perfect momentum sink assumption employed in the modelling of the lamella’s non-smooth dynamics. The lamella dynamics are observed to not convergence to fully periodic behaviour and the sensitivity of the lamella’s dynamics is considered to be the root cause. The velocity Verlet based structural solver does not provide fluid-structure coupling iterations, the inclusion of which, could improve the stability of the fluid solution. This endeavour establishes a foundation for the predictive numerical simulation of the OWM in the form of baseline numerical simulation results and a developed simulation framework.