ICAS Paper no. 282Nice, September [email protected]
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Benchmarking CEASIOM Software to Predict Flight Control and Flying
Qualities of the B-747
A. Da RonchThe University of Liverpool, UK
C. McFarlane, C. BeaverstockBristol University, UK
J. Oppelstrup, M. Zhang, A. RizziRoyal Institute of Technology, Sweden
ICAS Paper no. 282Nice, September [email protected]
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Introduction
• Contemporary aircraft conceptual designo Handbook methods, semi-empirical theoryo Need to recalibrate these empirical methods
• Augmented-stability & extended flight envelopeo More accurate flight dynamics modellingo Computational methods based on first principleo First-Time-Right with the FCS design architecture
ICAS Paper no. 282Nice, September [email protected]
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CEASIOMComputerized Environment for Aircraft Synthesis and
Integrated Optimization Methodso SimSAC project under the European Commission 6th
Framework Programmeo Integrates discipline-specific tools for conceptual design
to predict flying & handling qualities
http:/www.simsacdesign.eu
http:/www.ceasiom.com
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Test Case: Boeing 747
• Large 4-engined turbofan; 350+ pax
• Multiple control surfaces: Krueger LE flaps, triple-slotted TE
flaps
• Flight dynamics with FCSDT to evaluate different fidelity-
level approx
ICAS Paper no. 282Nice, September [email protected]
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Adaptive Fidelity CFD1. DATCOMo Semi-empirical
2. TORNADOo Vortex-Lattice method
3. EDGEo CFD solver
Fidelity CPU Time Geometry
ICAS Paper no. 282Nice, September [email protected]
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Adaptive Fidelity CFD1. DATCOMo Semi-empirical
2. TORNADOo Vortex-Lattice method
3. EDGEo CFD solver
• For conventional aircraft, estimate aero derivatives based on geometry details and flight conditions
• Suspect results for new configuration
• Handbook
ICAS Paper no. 282Nice, September [email protected]
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Adaptive Fidelity CFD1. DATCOMo Semi-empirical
2. TORNADOo Vortex-Lattice method
3. EDGEo CFD solver
http:/www.redhammer.se/tornado/
• Modified horse-shoe vortex singularity method
• Steady & low reduced-freq harmonic unsteady flows
• Prandtl-Glauert similarity role for compressibility
• Fuselage can be modelled
ICAS Paper no. 282Nice, September [email protected]
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Adaptive Fidelity CFD1. DATCOMo Semi-empirical
2. TORNADOo Vortex-Lattice method
3. EDGEo CFD solver
• 3D NS/Euler, compressible flow solver from FOI, Sweden
• Unstructured grids with arbitrary elements; node-centred FV
• Explicit Runge-Kutta integration to steady state
•Semi-implicit, dual-time method for unsteady problem
• Acceleration techniques, turbulence models, parallel implementation
ICAS Paper no. 282Nice, September [email protected]
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CFD Code - EDGEDeflection of control surfaces
1. Generation of a new grid for every new configuration of
deflected control surfaces
clean geometry
tens of grids needed
2. Transpiration BCs
only one single grid needed
limits on min/max deflection
ICAS Paper no. 282Nice, September [email protected]
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Challenges
1.How to automate grid generation for CFD?
2.How to do 100k CFD?
3.How to do S&C analysis early in design phase?
“...whether CFD can participate in the design process with sufficient speed to drive down the design cycle time”, Dawes et al.
ICAS Paper no. 282Nice, September [email protected]
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Challenges
1.How to automate grid generation for CFD?
2.How to do 100k CFD?
3.How to do S&C analysis early in design phase?
ICAS Paper no. 282Nice, September [email protected]
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From Geometry to CFD Grid (1)AcBuilder: sketch-pad
- Edit XML file to match new design
- Visual interpretation
ICAS Paper no. 282Nice, September [email protected]
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From Geometry to CFD Grid (2)
SUMO* (SUrface MOdeler)• Rapid generation of 3D water-tight geometry
• Automated generation of unstructured surface mesh
• Triangulation based on in-sphere criterion, better than
Delaunay, for skewed surfaces
• Volume mesh using TetGen
* http:/www.larosterna.com/dwfs.html
ICAS Paper no. 282Nice, September [email protected]
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From Geometry to CFD Grid (2)
SUMO surface grid
ICAS Paper no. 282Nice, September [email protected]
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From Geometry to CFD Grid (2)
SUMO volume grid
ICAS Paper no. 282Nice, September [email protected]
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TORNADO Geometry
Munk’s theory
Sink/source distribution
ICAS Paper no. 282Nice, September [email protected]
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Challenges
1.How to automate grid generation for CFD?
2.How to do 100k CFD?
3.How to do S&C analysis early in design phase?
ICAS Paper no. 282Nice, September [email protected]
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Flight Variables CoefficientsAoA Mach Beta Elev Rud Ail ... p q r CL CD Cm CY Cl Cn
- - - - - -
- - - - - -
- - - - - -
- - - - - -
- - - - - -
- - - - - -
- - - - - -
- - - - - -
Aerodynamic Table Format
Non-conventional controls
ICAS Paper no. 282Nice, September [email protected]
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Brute Force Approach
• Simple example; let’s assume:o 10 values for AoA, Mach, Beta, Elev, Rud, Ailo More than 100k entries needed in tableo 10 seconds each calculation using TORNADO
ICAS Paper no. 282Nice, September [email protected]
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Brute Force Approach
• Simple example; let’s assume:o 10 values for AoA, Mach, Beta, Elev, Rud, Ailo More than 100k entries needed in tableo 10 seconds each calculation using TORNADO
106 / (24 * 60 * 60) > 10 days
Brute force approach not feasible to fill-in aero
tables!
ICAS Paper no. 282Nice, September [email protected]
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Sampling & Data Fusion
Journal of Aircraft, 46 (3), 2009
Aerodynamic Tables
Flight Dynamics
Kriging
Existing
Table
Increments to
Design
Sampling
Database
New Design
Data Fusion for Aerodynamic Increments
ICAS Paper no. 282Nice, September [email protected]
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Sampling & Data Fusion
• STATIC effects:o Sampling for M-α-β dependence o Co-Kriging to calculate increments (controls)
• DYNAMIC effects:o No frequency dependenceo Alpha dependence onlyo Replace unsteady time-accurate with HB method? *o Stability derivatives from DATCOM
* AIAA Journal, 47 (4), 2009
ICAS Paper no. 282Nice, September [email protected]
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Challenges
1.How to automate grid generation for CFD?
2.How to do 100k CFD?
3.How to do S&C analysis early in design phase?
ICAS Paper no. 282Nice, September [email protected]
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FCSDT
FCSDT (Flight Control System Design Toolkit)• Design of the FCS, FCS architecture design
• Reliability analysis, failure mode analysis
• Control allocation, response simulation
• S&C analysis, HQ assessment, control laws design,
control laws definition, flight simulation
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Aerodynamic Predictions1.Low speed aerodynamics
2.Transonic regime
• DATCOM
• TORNADO
• TORNADO with compressibility correction
• EDGE in Euler mode
More comparisons in the paper; exp data from
Rodney, C.H., Nordwall, D.R., 1970
ICAS Paper no. 282Nice, September [email protected]
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Mach = 0.80
AoA = 1.0 deg
Positive elev deflection
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Results
1.Cruise condition
• Trim & Stability analysis
• Eigen-structure assignment for feedback
controller A + B *K• Flight Handling Qualities
2.Failed lower rudder segment
• Trim & Stability analysis
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Pole plot, Mach = 0.8
Short Period
Dutch-Roll
Phugoid
ICAS Paper no. 282Nice, September [email protected]
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Results
1.Cruise condition
• Trim & Stability analysis
• Eigen-structure assignment for feedback
controller A + B *K• Flight Handling Qualities
2.Failed lower rudder segment
• Trim & Stability analysis
Eigen value: -2 ± i *2 for Short Period mode
ICAS Paper no. 282Nice, September [email protected]
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Kα: gain value of feedback AoA to elevator
Kq: gain value of feedback pitch rate to elevator
ICAS Paper no. 282Nice, September [email protected]
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Results
1.Cruise condition
• Trim & Stability analysis
• Eigen-structure assignment for feedback
controller A + B *K• Flight Handling Qualities
2.Failed lower rudder segment
• Trim & Stability analysis
ICAS Paper no. 282Nice, September [email protected]
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Short Period mode
Eigenvalue: ƞ + i *ω T1/2 = ln(2) / |ƞ|
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Phugoid mode
ξ: damping ratio ωn: undamped circular freq
ICAS Paper no. 282Nice, September [email protected]
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Dutch Roll mode
ξ: damping ratio ωn: undamped circular freq
ICAS Paper no. 282Nice, September [email protected]
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Results
1.Cruise condition
• Trim & Stability analysis
• Eigen-structure assignment for feedback
controller A + B *K• Flight Handling Qualities
2.Failed lower rudder segment
• Trim & Stability analysis
Lower rudder segment failed at -10o for range of Mach numbers
ICAS Paper no. 282Nice, September [email protected]
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Conclusions• Aero tables for flight mechanics
o Automated generation of CFD grido From low-fidelity methods to CFDo Multiple control surfaceso Smart procedure to fuse data
• Test case: Boeing 747, trim analysis & poles ploto Cruise conditiono Failure analysis: lower rudder segment jammed
• Demonstratedo Robust process for S&C analysis in early designo CFD needed for good prediction for a realistic test case
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Future Works
• Flight manoeuvre replayo Aero table with dynamic derivatives from HBo Replay with CFDo When does prediction fail? * Unsteady effects?
• Need to review model for flight mechanicso System IDo Indicial (successfully used in gust analyses)o State Space
• Towards modelling of unsteady effects
* AIAA-2009-6273