Prediction of Helicopter Maneuver Loads Using a Fluid-Structure Analysis

Abstract

A fluid-structure analysis framework that couples computational fluid dynamics and computational structural dynamics is constructed to study the aeromechanics of a helicopter rotor system under maneuvering-flight conditions. The computational fluid dynamics approach consists of the solution of unsteady Reynolds-averaged Navier-Stokes equations for the near field of the rotor coupled with the dynamics of trailed vortex wake that is computed using a free-vortex method. The computational structural dynamics 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 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 peak-to-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 prediction of stall onset, reattachment, and shock-induced separation.