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

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

A. Da Ronch

The University of Liverpool, UK

C. McFarlane, C. Beaverstock

Bristol University, UK

J. Oppelstrup, M. Zhang, A. Rizzi

Royal Institute of Technology, Sweden

- Introduction
- Contemporary aircraft conceptual design
- Handbook methods, semi-empirical theory
- Need to recalibrate these empirical methods
- Augmented-stability & extended flight envelope
- More accurate flight dynamics modelling
- Computational methods based on first principle
- First-Time-Right with the FCS design architecture

- CEASIOM
- Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods
- SimSAC project under the European Commission 6th Framework Programme
- Integrates discipline-specific tools for conceptual design to predict flying & handling qualities
- http:/www.simsacdesign.eu
- http:/www.ceasiom.com

Objectives

CEASIOM main GUI

- 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

- Adaptive Fidelity CFD
- DATCOM
- Semi-empirical

- TORNADO
- Vortex-Lattice method

- EDGE
- CFD solver

- DATCOM

Fidelity

CPU Time

Geometry

- Adaptive Fidelity CFD
- DATCOM
- Semi-empirical

- TORNADO
- Vortex-Lattice method

- EDGE
- CFD solver

- DATCOM

- For conventional aircraft, estimate aero derivatives based on geometry details and flight conditions
- Suspect results for new configuration
- Handbook

- Adaptive Fidelity CFD
- DATCOM
- Semi-empirical

- TORNADO
- Vortex-Lattice method

- EDGE
- CFD solver
- http:/www.redhammer.se/tornado/

- DATCOM

- Modified horse-shoe vortex singularity method
- Steady & low reduced-freq harmonic unsteady flows
- Prandtl-Glauert similarity role for compressibility
- Fuselage can be modelled

- Adaptive Fidelity CFD
- DATCOM
- Semi-empirical

- TORNADO
- Vortex-Lattice method

- EDGE
- CFD solver

- DATCOM

- 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

- CFD Code - EDGE
- Deflection of control surfaces
- Generation of a new grid for every new configuration of deflected control surfaces
- clean geometry
- tens of grids needed
- Transpiration BCs
- only one single grid needed
- limits on min/max deflection

- Deflection of control surfaces

Challenges

How to automate grid generation for CFD?

How to do 100k CFD?

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.

Challenges

How to automate grid generation for CFD?

How to do 100k CFD?

How to do S&C analysis early in design phase?

From Geometry to CFD Grid (1)

- AcBuilder: sketch-pad
- Edit XML file to match new design
- Visual interpretation

- From Geometry to CFD Grid (2)
- SUMO* (SUrfaceMOdeler)
- 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

From Geometry to CFD Grid (2)

SUMO surface grid

From Geometry to CFD Grid (2)

SUMO volume grid

From Geometry to CFD Grid

TORNADO Geometry

TORNADO Geometry

Munk’s theory

Sink/source distribution

TORNADO Geometry

Challenges

How to automate grid generation for CFD?

How to do 100k CFD?

How to do S&C analysis early in design phase?

Aerodynamic Table Format

Non-conventional controls

- Brute Force Approach
- Simple example; let’s assume:
- 10 values for AoA, Mach, Beta, Elev, Rud, Ail
- More than 100k entries needed in table
- 10 seconds each calculation using TORNADO

- Brute Force Approach
- Simple example; let’s assume:
- 10 values for AoA, Mach, Beta, Elev, Rud, Ail
- More than 100k entries needed in table
- 10 seconds each calculation using TORNADO
- 106 / (24 * 60 * 60) > 10 days
- Brute force approach not feasible to fill-in aero tables!

Sampling & Data Fusion

Flight Dynamics

Database

Existing

Table

Increments to

Design

Aerodynamic Tables

Data Fusion for Aerodynamic Increments

Kriging

Sampling

New Design

Journal of Aircraft, 46 (3), 2009

- Sampling & Data Fusion
- STATIC effects:
- Sampling for M-α-β dependence
- Co-Kriging to calculate increments (controls)

- DYNAMIC effects:
- No frequency dependence
- Alpha dependence only
- Replace unsteady time-accurate with HB method? *
- Stability derivatives from DATCOM

* AIAA Journal, 47 (4), 2009

Challenges

How to automate grid generation for CFD?

How to do 100k CFD?

How to do S&C analysis early in design phase?

- 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

- Aerodynamic Predictions
- Low speed aerodynamics
- 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

CL vsα, Mach = 0.80

CD vs CL, Mach = 0.80

Cm vsα, Mach = 0.80

Mach = 0.80

AoA = 1.0 deg

Positive elev deflection

- Results
- Cruise condition
- Trim & Stability analysis
- Eigen-structure assignment for feedback controller A + B *K
- Flight Handling Qualities

- Failed lower rudder segment
- Trim & Stability analysis

Trimmed AoA

Trimmed elevator

Pole plot, Mach = 0.8

- Short Period

- Dutch-Roll

- Phugoid

- Results
- Cruise condition
- Trim & Stability analysis
- Eigen-structure assignment for feedback controller A + B *K
- Flight Handling Qualities

- Failed lower rudder segment
- Trim & Stability analysis

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

Kα: gain value of feedback AoA to elevator

Kq: gain value of feedback pitch rate to elevator

- Results
- Cruise condition
- Trim & Stability analysis
- Eigen-structure assignment for feedback controller A + B *K
- Flight Handling Qualities

- Failed lower rudder segment
- Trim & Stability analysis

Short Period mode

- Eigenvalue: ƞ + i *ωT1/2 = ln(2) / |ƞ|

Phugoid mode

- ξ: damping ratioωn: undamped circular freq

Dutch Roll mode

- ξ: damping ratioωn: undamped circular freq

- Results
- Cruise condition
- Trim & Stability analysis
- Eigen-structure assignment for feedback controller A + B *K
- Flight Handling Qualities

- Failed lower rudder segment
- Trim & Stability analysis

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

- Conclusions
- Aero tables for flight mechanics
- Automated generation of CFD grid
- From low-fidelity methods to CFD
- Multiple control surfaces
- Smart procedure to fuse data

- Test case: Boeing 747, trim analysis & poles plot
- Cruise condition
- Failure analysis: lower rudder segment jammed

- Demonstrated
- Robust process for S&C analysis in early design
- CFD needed for good prediction for a realistic test case

- Future Works
- Flight manoeuvre replay
- Aero table with dynamic derivatives from HB
- Replay with CFD
- When does prediction fail? * Unsteady effects?

- Need to review model for flight mechanics
- System ID
- Indicial (successfully used in gust analyses)
- State Space
- Towards modelling of unsteady effects

* AIAA-2009-6273