Transcript Document

Aircraft Dynamic And
STatic Aeroservoelastic Analysis Code
Summary
P.M.Mujumdar, A. Joshi, K Sudhakar
Aerospace Engineering, IIT Bombay
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Aircraft Dynamic And
STatic Aeroservoelastic Analysis Code
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ADASTAAC
ode
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WHAT IS ADASTAAC
• An INDUSTRY STANDARD STATE-of-ART Code for
Linear Static & Dynamic Aeroelastic Analysis of Aircraft
* Based on the Finite Element Method (Using existing FE software)
* A special computationally efficient direct (non-iterative) reduced
order formulation similar to the ELFINI Software
 Structural (FE) & Aerodynamic Computations run independent
of each other
* Specially tailor made for a design and development program,
particularly of combat aircraft
* Developed for the Aeronautical Development Agency (ADA)
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Features/Capabilities
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Complete aircraft in free flight: Wing-HT-VT-Fuselage
Wing-Fuselage, Wing-HT-VT aerodynamic interference modeled
Subsonic & supersonic speeds (no transonic capability at present)
Flexible & rigid load resultants & aero-elastic derivatives
Aero-elastic efficiencies of control surfaces
Complete flexible load and stress distribution
Divergence
Free vibration, mode shapes & flutter
Aeroelastic Loads during free flight dynamic maneuvers
Aero-Servo-Elastic dynamic response including actuator/sensor
modelling
• Introduction of externally computed aerodynamic pressures
• Editing of aerodynamic pressures to match externally input loads
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Features/Capabilities
• Steady Aerodynamics
* Vortex Lattice Method with mutual interference between all
components
* Fuselage modeling: 3 models supported. Model may require minor
tuning for special configurations. Model defines circulation over
fuselage as a function of circulation on wing root chord.
• Unsteady Aerodynamics
* Subsonic: Doublet Lattice Method (Acceleration Potential)
 Nonplanar interference
 Quartic approximation of kernel
 Steady part of kernel by VLM
 Analytical integration of improper integrals
* Supersonic: Doublet Point Method (Acceleration Potential)
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Features/Capabilities
• Free Vibration
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Eigen-problem formulated in monomial basis
Natural Frequencies & Modes for a solution case
No need to go to FE solution for different mass configurations
Accuracy depends on number of monomials and smoothing
• Flutter
* U-g & P-k Methods
* Mode Tracking Algorithms in U-g
 Frequency based sorting
 Complex Modal Assurance Criterion (right eigenvectors)
 Complex Bi-orthogonality of left and right eigenvectors
* Free/Clamped Analysis for Symm. & Anti-symm. BCs.
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Features/Capabilities
• Aero-servo-elastic Dynamic Response
* State Space Formulation
* Multiple Pole Pure Lag Rational Function Approximation for time
domain unsteady aerodynamics
* Two types of actuator models
 No Load
 With Finite impedance of the actuator considered
* Two levels of actuator transfer function
 Second order
 Fourth order
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TIMELINE
• 1992 – 1995
PHASE I
• 1997 - 2001
PHASE II
• Total work period = 3 + 4.5 = 7.5 years
* Effort
• Total funds
≈ 12 man years
= 2 million Rs.
• Code fully written by the team of 3 faculty members
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General Information
• Programming languages
* FORTRAN (f77 along with a few f90 extensions)
* MATLAB - for dynamic response
• Complete package available in source form.
* In-house written code for complete analysis
* Public Domain LAPACK routines for linear algebra
• Hardware platforms on which tested
* Pentium + Linux
* IBM RISC, Digital Alpha
• Extensive restart capability supported by database
• Memory management, simple input, easily readable output
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Some Statistics
• Total number of source lines
44,020
* ADASTAAC
33,416
* FINSTAAC
10,604
 (Comment lines not included,
 COMMON, PARAMETER etc through
INCLUDE
• Total number of COMMANDS
47
(basic unit of analysis)
• Total number of Subroutines
645
• Total number of files
70
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Excluding
LAPACK
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Code Organisation
• Modularity & Commands
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Functionally decomposed to modules (commands)
Intra-Command data transfer through database
Restart capability at Commands level
Special Commands to help debugging
• Data driven flow through analysis
* Flow controlled by command sequence given in input data
* Each command followed by data required for that command
* Commands execute by reading its data from file
 Read from data base. Written by other commands
 Execute its function
 Write to data base. To be read by other commands.
* Command dependency (Permissible sequences)
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Code Organisation
COMMAND Grouping
* General group
* Geometry group
* AE-Tree group
* FE-Tree group
* Solution group
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- Functions to support debugging, exploration
- Mesh, selection, monomial, tree, RCI creation
- Aerodynamic related analysis on AE-Tree
Estimate Cp & U, adjust/edit Cp & U
- FE related operations on FE-Tree
Smooth, Mass case, External load cases,
Load basis, displacement basis.
- “tree + mass case + external loads”
Inertia corrections, reduction to monomial
basis, divergence, free vibrations, flutter,
flight dynamic maneuvers, Aeroservoelastic
dynamic responses.
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Code Organisation
• Dependency of command groups
* General group commands have no hierarchy and can appear
anywhere to support debugging.
* Geometry  AE-Tree / FE-Tree  Solution group
• Dependency of commands within a group
• Extensive Error trapping supported
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Validation
Steady Aerodynamics
• Wings – Constant chord. Validated against DATCOM & ELFINI
- Mach no 0.0 to 2.0
- AR = 2 to 20
- Sweep = 00 to 600
• Delta Wings. Validated against DATCOM & ELFINI
- Mach no 0.0 to 2.0
- Sweep 600
- LCA wing planform.
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Wing-HT – (both rectangular) Validated against DATCOM
Wing-Fuselage – Qualitative checks
Wing-Fin – Qualitative checks
Control Surface loads – against DATCOM & ELFINI
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Validation (Contd.)
• Subsonic Unsteady Aerodynamics
* Rectangular wings (Literature)
 AR = 20, M = 0.0, k = 1.0
Flap oscillation, Expts
 AR = 12, M = 0.2, k = 0.0, 0.5 Heave, pitch
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Validation (Contd.)
• Static Aeroelasticity
* Divergence and efficiencies
 Rectangular wing – AR = large. Analytical results
(Free/clamped)
 Swept/delta plate wings - ELFINI
 Simplified LCA wing, fin & wing-fin - ELFINI
• Dynamic Aeroelasticity
* Free vibration & flutter
 Simplified LCA wing-fin, SYMM Case – NASTRAN, ELFINI
* Dynamic response
 Simplified LCA wing-fin, Replication of vibration & flutter
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