Benchmarking CEASIOM Software to Predict Flight Control and Flying Qualities of the B-747

ICAS Paper no. 282Nice, September [email protected]

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http://www.liv.ac.uk/


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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


http://www.simsacdesign.org/


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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



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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


http://www.simsacdesign.org/


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Objectives



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CEASIOM main GUI



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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



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Adaptive Fidelity CFD1. DATCOMo Semi-empirical

2. TORNADOo Vortex-Lattice method

3. EDGEo CFD solver

Fidelity CPU Time Geometry



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3. EDGEo CFD solver

• For conventional aircraft, estimate aero derivatives based on geometry details and flight conditions

• Suspect results for new configuration

• Handbook



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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



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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



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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



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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.



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Challenges






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From Geometry to CFD Grid (1)AcBuilder: sketch-pad

- Edit XML file to match new design

- Visual interpretation



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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



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SUMO surface grid



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SUMO volume grid



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From Geometry to CFD Grid



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TORNADO Geometry



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TORNADO Geometry

Munk’s theory

Sink/source distribution



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TORNADO Geometry



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Challenges






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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



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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



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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!



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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



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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



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Challenges






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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



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CL vs α, Mach = 0.80



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CD vs CL, Mach = 0.80



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Cm vs α, Mach = 0.80



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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




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Trimmed AoA



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Trimmed elevator



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Pole plot, Mach = 0.8

Short Period

Dutch-Roll

Phugoid



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Results

1.Cruise condition






Eigen value: -2 ± i *2 for Short Period mode



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Kα: gain value of feedback AoA to elevator

Kq: gain value of feedback pitch rate to elevator



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Results

1.Cruise condition








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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



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Dutch Roll mode

ξ: damping ratio ωn: undamped circular freq



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Results

1.Cruise condition






Lower rudder segment failed at -10o for range of Mach numbers



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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


Documents

Benchmarking CEASIOM Software to Predict Flight Control and Flying Qualities of the B-747