The wake geometry and unsteady loading of an articulated three-degree-of freedom blade with hinge off-sets in hover with gust and descent flight is examined. It has been well documented that blade tip vortices are the most dominant structures in the rotor wake. These vortex structures induce high local flow velocities and contribute significantly to the unsteadiness encountered by the rotor blade. Specific types of interactions between blades and tip vortices from preceding blades can produce high-localized pressure fluctuations over the blade surface. It is clearly desirable to include all three aerodynamic force and moment components together with the rotor blade structural dynamics in an integrated solution process. So for the best results about strongly coupled dynamics with unsteady aerodynamics, this can be accomplished by replacing the traditional blade-element methods and prescribed wake model with the unsteady time-marching free wake scheme. Especially for the descent flight as well as hover flight, it is expected that, for an unstable dynamics mode, the disturbance will be generated naturally from the wake.
This paper will include a discussion of the linear and non-linear rotor dynamics equation in hover and vertical flight coupled with time-marching free wake scheme.
