The key objectives of this paper are to assess the accuracy and the validity of our current aerodynamic analysis tools in predicting the unsteady flow field generated by helicopter rotors and to investigate their applicability to the future design problems. A Reynolds-Averaged Naiver-Stokes (RANS) solver with various turbulence models has been used with necessary modifications for the computation of all test cases. Dynamic stall and massive separation, which are physical phenomena

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... of helicopter flows, are analyzed first using RANS methodology, and Detached Eddy Simulation (DES) is applied to the simulation of massive separation and compared to corresponding RANS solutions. The periodic nature of the helicopter flowfield strongly motivates the application of Time-Spectral (TS) approach for unsteady RANS computations. In this paper, the TS method is applied to simulate actual flight conditions of the UH-60A helicopter and is verified to be a fast and efficient algorithm which maintains the same level of accuracy as the timeaccurate approach. In addition, the TS method also provides great potential for adjoint based design optimization of helicopter rotors as the governing equations can be reduced to a periodic steady state.