Simulation of Rotor-Empennage Interactional Aerodynamics in Comparison to Experimental Data

Abstract

Aerodynamic interactions between the rotor and the empennage can have a significant impact on steady and unsteady loads and often result in challenges in a rotorcraft design phase. In the present work, numerical analysis of rotor-empennage aerodynamic interactions were compared to full-scale flight test data with respect to steady and unsteady interactional aerodynamic effects. The flight tests provided loads for a low-empennage and a T-Tail configuration for various forward flight velocities. For the T-Tail configuration, additional pressure sensors provided validation data for steady and unsteady interaction effects. The numerical analysis was focused on an unsteady panel method, complemented by high-fidelity CFD/CSM-coupling results for a level flight state. Furthermore, a supplemental validation of the unsteady panel method was performed against an isolated wing-vortex interaction experiment. The flight test data revealed a strong asymmetry in mean empennage loads, which increases with forward flight velocity. The numerical analysis showed coherent results with a slight over-prediction in high-speed. The T-Tail configuration is furthermore subject to 3D effects between the vertical- and horizontal tail. These effects influence pressure and load-distributions on the T-Tail, which was captured by both numerical methods. The general characteristics of the unsteady pressure signatures were captured by both methods. The panel method showed slightly better representation of amplitude.