Aeromechanic and Aeroacoustic Predictions of the Boeing SMART Rotor Using Coupled CFD/CSD Analysis

A computational study has been done on the Boeing Active Flap SMART Rotor using the computational tools developed at Georgia Institute of Technology, The Pennsylvania State University, and Northern Arizona University under the DARPA Helicopter Quieting Program. These tools included modifications to the Computational Fluid Dynamics code OVERFLOW for elastic rotors, higher order numerical schemes, advanced turubulence models, and acoustics. Further additions to the solver have been made at Georgia Tech and AFDD to model the SMART rotor. The multibody finite element tool DYMORE is used to compute the structural dynamics of the SMART rotor. The DYMORE model for the SMART rotor models the flap as an elastic rotor with its own lifting line and is connected to the main rotor by elastic connetors. OVERFLOW and DYMORE are coupled using modified FSI formated files. The Ffowcs Williams-Hawkings acoustic analogy solver PSUWOPWOP is used to compute the rotor noise using on blade and off blade acoustic data surfaces. Computed and experimental structural loads are compared for a zero flap actuation and 3P flap actuation case in moderate speed cruise flight. Acoustic calculations for these cases showed good overall correlation of the negative pressure peak but an over prediction of the positive pressure between blade passages using nonrotating permeable acoustic data surfaces. Acoustic reflections were not accounted for and expected to improve predictions.