26th INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES PREDICTION OF HELICOPTER MANEUVER LOADS USING A COUPLED CFD/CSD ANALYSIS

A fluid-structure analysis framework which couples Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) is constructed to study the aero-mechanics of a helicopter rotor system under maneuvering flight conditions. The CFD approach consists of the solution of Unsteady Reynolds Average Navier Stokes (URANS) equations for the near-field of the rotor coupled with the dynamics of trailed vortex wake that are computed using a free vortex method. The CSD approach uses a multibody Finite Element method to model the rotor hub and blades. The analysis framework is used to study the Utility Tactical Transport Aerial System (UTTAS) pull-up maneuver of the UH-60A helicopter. Results shown illustrate the correlation of predicted performance, aerodynamic and structural dynamic loading with measured flight test data. The normal load factor and the peakto-peak structural and aerodynamic loading show good correlation with flight test data, indicating that the analysis framework is suitable for preliminary design purposes. Important phenomena such as advancing blade transonic effects and retreating blade flow separation are predicted satisfactorily. However, deficiencies are noted in the accurate resolution of stall incidence, reattachment and shock induced separation.