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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

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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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747


CEASIOM main GUI Flying Qualities of the B-747


  • Test Case: Boeing 747 Flying Qualities of the B-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 Flying Qualities of the B-747

    • DATCOM

      • Semi-empirical

    • TORNADO

      • Vortex-Lattice method

    • EDGE

      • CFD solver

Fidelity

CPU Time

Geometry


  • Adaptive Fidelity CFD Flying Qualities of the B-747

    • DATCOM

      • Semi-empirical

    • TORNADO

      • Vortex-Lattice method

    • EDGE

      • CFD solver

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

  • Suspect results for new configuration

  • Handbook


  • Adaptive Fidelity CFD Flying Qualities of the B-747

    • DATCOM

      • Semi-empirical

    • TORNADO

      • Vortex-Lattice method

    • EDGE

      • 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


  • Adaptive Fidelity CFD Flying Qualities of the B-747

    • DATCOM

      • Semi-empirical

    • TORNADO

      • Vortex-Lattice method

    • EDGE

      • 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


  • CFD Code - EDGE Flying Qualities of the B-747

    • 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


Challenges Flying Qualities of the B-747

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 Flying Qualities of the B-747

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) Flying Qualities of the B-747

  • AcBuilder: sketch-pad

  • Edit XML file to match new design

  • Visual interpretation


  • From Geometry to CFD Grid (2) Flying Qualities of the B-747

  • 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) Flying Qualities of the B-747

SUMO surface grid


From Geometry to CFD Grid (2) Flying Qualities of the B-747

SUMO volume grid


From Geometry to CFD Grid Flying Qualities of the B-747


TORNADO Geometry Flying Qualities of the B-747


TORNADO Geometry Flying Qualities of the B-747

Munk’s theory

Sink/source distribution


TORNADO Geometry Flying Qualities of the B-747


Challenges Flying Qualities of the B-747

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 Flying Qualities of the B-747

Non-conventional controls


  • Brute Force Approach Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

How to automate grid generation for CFD?

How to do 100k CFD?

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


  • FCSDT Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747vsα, Mach = 0.80


CD Flying Qualities of the B-747vs CL, Mach = 0.80


Cm Flying Qualities of the B-747vsα, Mach = 0.80


Mach = 0.80 Flying Qualities of the B-747

AoA = 1.0 deg

Positive elev deflection


  • Results Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747AoA


Trimmed elevator Flying Qualities of the B-747


Pole plot, Mach = 0.8 Flying Qualities of the B-747

  • Short Period

  • Dutch-Roll

  • Phugoid


  • Results Flying Qualities of the B-747

  • 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


K Flying Qualities of the B-747α: gain value of feedback AoA to elevator

Kq: gain value of feedback pitch rate to elevator


  • Results Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • Eigenvalue: ƞ + i *ω T1/2 = ln(2) / |ƞ|


Phugoid Flying Qualities of the B-747 mode

  • ξ: damping ratio ωn: undamped circular freq


Dutch Roll mode Flying Qualities of the B-747

  • ξ: damping ratio ωn: undamped circular freq


  • Results Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • 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 Flying Qualities of the B-747

  • 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


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