Coupling Mid-Fidelity Aerodynamics and Multibody Dynamics for the Aeroelastic Analysis of Rotary-Wing Vehicles

A mid-fidelity aerodynamic solver based on the vortex particle method for wake modeling, DUST, is coupled through the partitioned multi-physics coupling library preCICE to a multibody dynamics code, MBDyn, to improve the accuracy of aeroelastic numerical analysis performed on rotary-wing vehicles. In this paper, the coupled tool is firstly validated by solving simple fixed-wing and rotary-wing problems from the open literature. The transient roll maneuver of a complete tiltrotor aircraft is then simulated, to show the capability of the coupled solver to analyze the aeroelasticity of complex rotorcraft configurations. Simulation results show the importance of the accurate representation of rotary wing aerodynamics provided by the vortex particle method for loads evaluation, aeroelastic stability assessment, and analysis of transient maneuvers of aircraft configurations characterized by complex interactional aerodynamics. The limited computational effort required by the mid-fidelity aerodynamic approach represents an effective trade-off in obtaining fast and accurate solutions that can be used for the preliminary design of novel rotary-wing vehicle configurations.

Development of a quasi-linear parameter varying model for a tiltrotor aircraft

The research presented in this paper focuses on the development of a quasi-Linear Parameter Varying (qLPV) model for the XV-15 tiltrotor aircraft. The specific category of qLPV modeling technique, known as the model stitching technique, is employed to model the time-varying dynamics of XV-15 tiltrotor aircraft over the entire flight envelope. In this modeling approach, discrete linear state-space models are interpolated through lookup tables as function of scheduling parameters with the implementation of nonlinear equations of motion. The XV-15 qLPV model is configured with four scheduling parameters: altitude, nacelle incidence angle, wing flap angle and velocity. Additionally, a computational complexity analysis is presented. In particular, computational sensitivity of qLPV models configured with lookup tables to number of states and number of scheduling parameters is demonstrated. This is done to show the feasibility of real-time implementation of qLPV models with increasing fidelity (number of states) and expanding dynamic flight envelope (number of scheduling parameters).

Keen Investigation of the Electromagnetic Scattering Characteristics of Tiltrotor Aircraft Based on Dynamic Calculation Method

To study the radar characteristics of the tiltrotor aircraft when considering rotor rotation and tilting actions, a dynamic calculation method (DCM) based on physical optics and physical theory of diffraction is presented. The results show that the radar cross section of a single rotor is dynamic and periodic when it rotates, while increasing the rotation speed can shorten this period. At a fixed tilt angle, the overall radar cross section of the cabin plus rotor still exhibits various dynamic characteristics at different azimuths when considering the rotation of the rotor. Increasing the tilt angle can better improve the electromagnetic scattering level of the rotor, but this easily makes the cabin and the outer end of the wing become a new source of strong scattering. In the heading direction, the dynamic radar cross section of the aircraft under a larger azimuth angle is lower when the cabin tilts from horizontal to vertical position. The presented DCM is feasible and effective to obtain the electromagnetic scattering characteristics of tiltrotor aircraft.

Interaction effects on the conversion corridor of tiltrotor aircraft

This paper presents an aeromechanics investigation of tiltrotor aircraft through the conversion regime of flight. The effects of the rotors-on-wing, rotors-on-empennage and wing-on-empennage interactions were investigated singularly and collectively to assess their impacts on trim behaviour, performance and conversion boundaries. The rotors-on-wing download was found to be dominant in the prediction of hover and low-speed flight performance and had a degrading effect overall. The fuselage pitch attitude and stick position were found to be significantly affected by the empennage interaction cases throughout the conversion domain. The large flap/flaperon settings used to alleviate the rotor download contributed considerably to the low-speed trim behaviour. The conversion boundaries were found to be insensitive to all the interaction cases, though the min-speed boundary was reduced marginally due to the wing-on-empennage interaction. The results showed that the combined interactions were important factors to accurately predict the trim behaviour and aircraft performance throughout the conversion corridor.