Rotorcraft Simulations with Coupled Flight Dynamics, Free Wake, and Acoustics

Open Access
- Author:
- Saetti, Umberto
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 18, 2016
- Committee Members:
- Joseph Francis Horn, Thesis Advisor/Co-Advisor
Kenneth Steven Brentner, Committee Member
George A Lesieutre, Committee Member - Keywords:
- rotorcraft
noise
control
control systems
dynamic inversion
feedback
flight dynamics
free wake
CHARM
PSUHeloSim
PSUWOPWOP - Abstract:
- This study presents the integration of a flight simulation code (PSUHeloSim), a high fidelity rotor aeromechanics model with free wake (CHARM Rotor Module), and an industry standard noise prediction tool (PSU-WOPWOP) into a comprehensive noise prediction system. The flight simulation uses a Dynamic Inversion autonomous controller to follow a prescribed trajectory for both steady and maneuvering flight conditions. The aeromechanical model calculates blade loads and blade motion that couple to the vehicle flight dynamics with suitable resolution to allow high fidelity acoustics analysis (including prediction of blade-vortex interaction (BVI) noise). The blade loads and motion data is sent to PSU-WOPWOP in a post-processing step to predict external noise. Particular attention is paid to the development of PSUHeloSim and to the enhancement of the closed-loop response characteristics of the coupled simulation. Specifically, is studied the use of reduced-order linear models, derived by linearization of the coupled simulation, in the feedback linearization of the Dynamic Inversion controller in different flight conditions. The different reduced-order models obtained are compared by the use of eigenvalue analysis and frequency response in order to link their differences to physical phenomena occuring in the coupled simulation. A validation of these reduced-order models is provided by performing a frequency sweep of the coupled simulation. Finally their effectiveness in the feedback linearization loop is evaluated by analysing the closed loop time response of the coupled simulation to the coupling. The coupled analysis is being used to evaluate the influence of flight path on aircraft noise certification metrics like EPNL and SEL for various rotorcraft in work for the FAA. The software was used to analyze the acoustic properties of a blade planform similar to the Blue Edge rotor blades developed by DLR and Airbus Helicopters - predicting BVI noise reduction as compared to more conventional blade geometries on the same order as that reported for the Blue Edge rotor.