An assessment of the long-age unsteady rotor hub wake physics for empennage analysis

In addition to providing a comprehensive review and presentation of state-of-the-art experimental and computational efforts concerning rotor hub flows, this paper presents evidence that both experimental and computational capabilities are ready to foster the physical understanding of the long-age unsteady wake due to rotor hubs. A primary asset of this work is to demonstrate that two different rotor hub configurations show common characteristics of the underlying flow physics. The results of the Georgia Tech computations, when correlated with the experimental data from Penn State University, on two very different four-bladed hub configurations imply that the features of these long-age wakes (in the region where the vehicle tail would be located) may be captured with current computational solvers. This has significant implications in the rotorcraft industry's ability to tackle unsteady aerodynamic and aeroelastic phenomena that degrade performance and component life on the empennage of the vehicle. The necessity of experimental evaluations at component supercritical Reynolds numbers is also confirmed, suggesting the need for large wind tunnel or water tunnel campaigns.