Two dimensional numerical analysis of Darrieus turbine is carried out with an Unsteady Reynolds-Averaged Navier- Stokes (URANS) equation and a structured mesh configuration using overset grid approach. It is confirmed that the calculations are in agreement with the experimental results for the tip speed ratio more than two at which the maximum power coefficient is obtained by the experiment. It is possible to solve the flow field around the turbine by the URANS in reasonable calculation time and the result practical enough is obtained in the flow field where the tip speed ratio is comparatively high and the separation is small.
