Computational Simulation and Analysis of Bell Boeing Quad Tiltrotor Aero Interaction

The unsteady flow field and aerodynamic performance of the Bell's wind tunnel test model of the Bell Boeing Quad tiltrotor are predicted and analyzed using a Navier-Stokes computational fluid dynamics (CFD) solver. The Quad tiltrotor contains both front and rear rotor and wing systems, which create aerodynamic interference and periodic time-dependent loadings for the aircraft in various flight conditions. In this study, interference effects of the Quad tiltrotor in two critical flight conditions, an airplane mode and a transition mode at 75-deg nacelle tilt angle, are numerically investigated. Predicted aerodynamic performance and airloads on the Quad tiltrotor components are analyzed and compared with the Bell Helicopter's COPTER estimates. The unsteady velocity field induced by the front rotor system is extracted from the Quad tiltrotor simulation, which is required by COFFER code in the subsequent aeroelastic analysis to predict oscillatory loads and vibrations.