Abstract: Unsteady viscous flows of a microcoaxial rotor are simulated and studied using moving overlapped grids and the dualtime stepping method. We discuss the small space between the up- and down-rotor and large flow viscosity, and introduce a sliding mesh based on moving overlapped grids, which ensure accurate exchange of flow information. Micro-single rotor flows with a low Reynolds number are calculated. The results are consistent with experimental results, showing effectiveness of the algorithm. Microcoaxial rotor flows are then simulated with this method. The results indicate that the blade tip vortex, which moves down in a spiral way, plays a leading role in microcoaxial rotor flows. It makes the total thrust of the rotor periodic due to its interaction with the rotary rotor.

Key words: micro-coaxial rotor, moving overlapped grids, sliding mesh