An Indirect Stability Method Applied to Whirl Flutter using Computational Fluid Dynamics Actuator Disc Models

A recently developed indirect eigenvalue method is applied to propeller whirl flutter stability using computational fluid dynamics. The use of computationally efficient actuator disc models is compared to actuator blade and wall-resolved models. Actuator disc and blade results are confirmed to be both mesh and time-step independent. Actuator disc models produce stability results that closely emulate analytic quasi-steady approximations, whereas actuator blade models are observed to most closely resemble analytic unsteady approximations. The wall-resolved model of the propeller produces the most accurate results but is between three to four orders of magnitude more computationally expensive than the actuator disc model. It is concluded that actuator disc models could be used in concert with the indirect eigenvalue method to compute eigenvalues of low-frequency modes with reasonable accuracy, especially in situations with complicated fluid dynamics and disparate time scales where wall-resolved models are currently computationally infeasible.