Effects of Transition Modeling on the Simulation of Helicopter Rotor Hubs

No abstract. Part of Introduction: Helicopter rotor hubs are geometrically complex components that experience a wide rage of aerodynamic behaviors and flow physics. This includes strong unsteadiness, large amounts of separation, laminar-turbulent transition, and interactional aerodynamic behaviors (Ref. 1). At high forward flight speeds (high advance ratios), the parasitic drag of the hub accounts for O(30 percent) of the total power required to fly (Ref. 1). A common method for characterizing this contribution is the hub drag factor, Kf e, which correlates the flat-plate area of the hub with the helicopter gross weight and functions as a technology factor (Ref. 2). In a recent assessment of needs for future vertical lift systems, Ormiston suggested that the hub drag factor needs to be reduced from the current state of the art of Kf e = 0:5 down to a value 0.2 (Ref. 3).