SLIDE 1 Further Results Further Results
- f Soft-Inplane Tiltrotor
- f Soft-Inplane Tiltrotor
Aeromechanics Investigation Aeromechanics Investigation Using Two Multibody Using Two Multibody Analyses Analyses
Pierangelo Masarati Pierangelo Masarati
Assistant Professor Assistant Professor Dipartimento di Ingegneria Aerospaziale Dipartimento di Ingegneria Aerospaziale Politecnico di Milano (Italy) Politecnico di Milano (Italy)
AHS International 60th Annual Forum & Technology Display AHS International 60th Annual Forum & Technology Display Baltimore, MD - Inner Harbor Baltimore, MD - Inner Harbor June 7-10, 2004 June 7-10, 2004
SLIDE 2 Authors and Contributors Authors and Contributors
David J. Piatak
NASA Langley Research Center NASA Langley Research Center
Jeffrey D. Singleton
Army Research Laboratory Army Research Laboratory
Giuseppe Quaranta
Politecnico di Milano Politecnico di Milano
SLIDE 3 Outline Outline
Objectives and Approach
- Experimental Model Description
Experimental Model Description
- Multibody Dynamics Analyses
Multibody Dynamics Analyses
Key Analytical Results
- Isolated Blade & Hub Results
Isolated Blade & Hub Results
Control System Couplings
- Hover Performance & Stability
Hover Performance & Stability
Forward Flight Stability
- Selected Nonlinear Analysis Issues
Selected Nonlinear Analysis Issues
Concluding Remarks
SLIDE 4 Objectives Objectives
- Compare multibody analytical techniques
Compare multibody analytical techniques
- Develop fundamental understanding of strengths,
Develop fundamental understanding of strengths, weaknesses, and capabilities of two different codes weaknesses, and capabilities of two different codes 2.
- 2. Assess prediction capabilities
Assess prediction capabilities
- Compare response, loads, and aeroelastic stability in
Compare response, loads, and aeroelastic stability in hover & forward flight. hover & forward flight.
Analysis vs. analysis
Analysis vs. experiment
3.
- 3. Assess code/user fidelity
Assess code/user fidelity
1.
- 1. Two different multibody codes
Two different multibody codes
2.
- 2. Two different researchers
Two different researchers
3.
- 3. Contrasting two codes helps eliminate errors in modeling
Contrasting two codes helps eliminate errors in modeling
SLIDE 5
Experimental Model Experimental Model
Wing & Rotor Aeroelastic Test System (WRATS) Wing & Rotor Aeroelastic Test System (WRATS)
Tested in the Rotorcraft Hover Test Facility and the Transonic Tested in the Rotorcraft Hover Test Facility and the Transonic Dynamics Tunnel at NASA Langley Research Center Dynamics Tunnel at NASA Langley Research Center
Semi-Articulated Semi-Articulated Soft-Inplane Hub Soft-Inplane Hub (SASIP) (SASIP) 4 blades 4 blades articulated articulated soft-inplane soft-inplane elastomeric lag elastomeric lag damper damper
SLIDE 6 Multibody Multibody Analyses Analyses
- Time domain - analyze via virtual experiments
Time domain - analyze via virtual experiments
- Can model components and mechanical
Can model components and mechanical effects not typically included with effects not typically included with comprehensive rotor analyses comprehensive rotor analyses
1. 1.Hydraulic components Hydraulic components 2. 2.Mechanical joints Mechanical joints 3. 3.Free-play in linkages Free-play in linkages
3. 3.No fixed-hub assumption No fixed-hub assumption
SLIDE 7 Analytical Models & Analysts Analytical Models & Analysts
- MBDyn - MultiBody Dynamics
MBDyn - MultiBody Dynamics
- Developed by (a team led by)
Developed by (a team led by)
- Prof. Paolo Mantegazza, Politecnico di Milano
- Prof. Paolo Mantegazza, Politecnico di Milano
- WRATS-SASIP analyzed by Pierangelo Masarati
WRATS-SASIP analyzed by Pierangelo Masarati and Giuseppe Quaranta and Giuseppe Quaranta
2. 2.DYMORE DYMORE
1.
- 1. Developed by (a team led by)
Developed by (a team led by)
- Prof. Olivier Bauchau, Georgia Tech
- Prof. Olivier Bauchau, Georgia Tech
2.
- 2. WRATS-SASIP analyzed by Dave Piatak and Jinwei
WRATS-SASIP analyzed by Dave Piatak and Jinwei Shen Shen
SLIDE 8 MBDyn - Analytical Model MBDyn - Analytical Model
Swashplate mechanics
Hydraulic actuators
3.
Blades as composite- ready beams, with blade ready beams, with blade element aerodynamics element aerodynamics
4.
- 4. Wing as modal element,
Wing as modal element, with state-space with state-space aerodynamics aerodynamics
Analysis includes: Analysis includes:
Conventional WRATS Model
SLIDE 9 DYMORE - Analytical Model DYMORE - Analytical Model
Blade Model Blade Model
4 element FEM 4 element FEM Lifting line Lifting line 3D inflow model 3D inflow model Highly twisted: 34 Highly twisted: 34 degrees from root to tip degrees from root to tip Structural and Structural and geometrical properties geometrical properties tuned to match WRATS tuned to match WRATS SASIP ground vibration SASIP ground vibration test results test results
SLIDE 10
DYMORE Simulation Example DYMORE Simulation Example
SLIDE 11 Blade Modal Analysis Blade Modal Analysis
All analyses consistent All analyses consistent Results agree with experiment Results agree with experiment
108.49 108.49 106.58 106.58 103.50 103.50 107.94 107.94 T1 T1 61.45 61.45 62.43 62.43 64.20 64.20 61.15 61.15 F3 F3 18.51 18.51 19.37 19.37 20.01 20.01 21.7 21.7 F2 F2 6.46 6.46 6.32 6.32 6.43 6.43 6.46 6.46 L1 L1 0.69 0.69 0.67 0.67 0.76 0.76
F1 DYMORE DYMORE MBDyn MBDyn UMARC UMARC Measured Measured Mode Mode
SLIDE 12 Control System Couplings Control System Couplings
Typically difficult to
- model. Elastic
- model. Elastic
deformation can have a deformation can have a significant contribution. significant contribution.
Non-linear modeling - classical analyses classical analyses typically use constant or typically use constant or tabulated lookup tabulated lookup coefficients. coefficients.
Multibody codes capture nonlinear effect. nonlinear effect.
SLIDE 13 Hover Run-up Hover Run-up
- Current analytical model is a
Current analytical model is a simple, constant stiffness simple, constant stiffness equivalent spring hinge equivalent spring hinge
SLIDE 14 Hover Hover Performance Performance
Blade elasticity and geometrical cross-couplings geometrical cross-couplings greatly influence greatly influence performance predictions performance predictions
SLIDE 15
Hover Dynamics Hover Dynamics
Transient time-series correlate with Transient time-series correlate with frequency analysis frequency analysis Linear wind-up Linear wind-up
SLIDE 16
Forward Flight Stability Forward Flight Stability
Comparison of Comparison of generic soft- generic soft- stiff inplane stiff inplane wing mode wing mode damping, damping, Windmilling Windmilling configuration configuration
SLIDE 17
Forward Flight Stability Forward Flight Stability
Comparison of Comparison of generic soft-stiff generic soft-stiff inplane wing inplane wing mode damping in mode damping in powered and powered and windmill. windmill. Windmilling case Windmilling case correlates well. correlates well. Initial results for Initial results for powered mode powered mode did not (no drive did not (no drive system system dynamics) dynamics)
SLIDE 18
Powered Flight Damping Bucket Powered Flight Damping Bucket
Experimental evidence of high damping in wing beam mode Experimental evidence of high damping in wing beam mode in powered flight, with in powered flight, with low damping bucket low damping bucket around zero around zero torque torque High damping found in coupling with drive train dynamics High damping found in coupling with drive train dynamics Possible bucket explanation found by considering deadband Possible bucket explanation found by considering deadband in drive train in drive train
SLIDE 19
Powered Flight Damping Bucket Powered Flight Damping Bucket
Stiff-inplane experimental results have generally show only Stiff-inplane experimental results have generally show only small differences in wing damping between powered and wind- small differences in wing damping between powered and wind- milling flight mode. milling flight mode. Soft-inplane experimental results have significant differences. Soft-inplane experimental results have significant differences. Reason is ‘chance’ coupling of drive dynamics with wing: Reason is ‘chance’ coupling of drive dynamics with wing:
SLIDE 20
Powered Flight Damping Bucket Powered Flight Damping Bucket
Deadband yields windmill- Deadband yields windmill- like damping like damping Soft mast slope controls Soft mast slope controls bucket width bucket width
SLIDE 21
Powered Flight Damping Bucket Powered Flight Damping Bucket
SLIDE 22
Powered Flight Damping Bucket Powered Flight Damping Bucket
Damping Damping peaks at peaks at bucket bucket borders may borders may be explained be explained with with identification identification close to close to deadband deadband transition transition
SLIDE 23 Concluding Remarks Concluding Remarks
Multibody codes can:
- successfully model complex systems
successfully model complex systems
- improve predictions of rotorcraft dynamic behavior
improve predictions of rotorcraft dynamic behavior
- proficiently address nonlinearity issues
proficiently address nonlinearity issues
Next steps are:
1.
- 1. Conversion / maneuver simulations
Conversion / maneuver simulations
2.
- 2. Hub/blade maneuver loads correlation
Hub/blade maneuver loads correlation
3.
- 3. Parametric study of SASIP
Parametric study of SASIP
SLIDE 24 Special Thanks To - Special Thanks To -
Giampiero Bindolino
(Politecnico di Milano, Dipartimento di Ingegneria Aerospaziale) (Politecnico di Milano, Dipartimento di Ingegneria Aerospaziale)
Mark W. Nixon
(ARL: Army Research Laboratory, Vehicle Technology Directorate) (ARL: Army Research Laboratory, Vehicle Technology Directorate)
Jinwei Shen
(NIA: National Institute of Aerospace) (NIA: National Institute of Aerospace)
