Numerical Analysis of Dynamic Stall for Different Helicopter Rotor Flight Conditions

Helicopter reaches its flight domain limit at high-thrust forward flight or maneuver with high load factors because of dynamic stall. This phenomenon is due to complex unsteady three-dimensional flow separation mechanisms that occur on the retreating blade. These flow separations can be of different natures depending on the flight conditions. This paper proposes to investigate numerically two significantly different cases of dynamic stall on a helicopter rotor in forward flight. The results show that the numerical simulation can capture the variations of section pitching moment associated with dynamic stall, for each of these two flight cases. A deep analysis of the numerical results allows to identify distinct flow separation regions appearing on the rotor disk. Similarities and differences are highlighted between the dynamic stall characteristics of these two rotor flight conditions.