1. STatic Aeroservoelastic Analysis Code
Aircraft Dynamic And
STatic Aeroservoelastic Analysis Code
Summary
P.M.Mujumdar, A. Joshi, K Sudhakar
Aerospace Engineering, IIT Bombay
4/15/2019

2. STatic Aeroservoelastic Analysis Code
Aircraft Dynamic And
STatic Aeroservoelastic Analysis Code
4/15/2019

3. ADASTAAC
ode
4/15/2019

4. 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)
4/15/2019

5. Features/Capabilities
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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6. 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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7. Features/Capabilities
Free Vibration
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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8. 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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9. TIMELINE 1992 – 1995 PHASE I 1997 - 2001 PHASE II
Total work period = = years
Effort ≈ 12 man years
Total funds = 2 million Rs.
Code fully written by the team of 3 faculty members
4/15/2019

10. 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
4/15/2019

11. 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
(basic unit of analysis)
Total number of Subroutines
Total number of files
Excluding
LAPACK
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12. Code Organisation Modularity & Commands
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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13. Code Organisation COMMAND Grouping
General group - Functions to support debugging, exploration
Geometry group - Mesh, selection, monomial, tree, RCI creation
AE-Tree group - Aerodynamic related analysis on AE-Tree
Estimate Cp & U, adjust/edit Cp & U
FE-Tree group - FE related operations on FE-Tree
Smooth, Mass case, External load cases,
Load basis, displacement basis.
Solution group - “tree + mass case + external loads”
Inertia corrections, reduction to monomial basis, divergence, free vibrations, flutter,
flight dynamic maneuvers, Aeroservoelastic dynamic responses.
4/15/2019

14. 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
4/15/2019

15. 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
Sweep 600
LCA wing planform.
Wing-HT – (both rectangular) Validated against DATCOM
Wing-Fuselage – Qualitative checks
Wing-Fin – Qualitative checks
Control Surface loads – against DATCOM & ELFINI
4/15/2019

16. Validation (Contd.) Subsonic Unsteady Aerodynamics
Rectangular wings (Literature)
AR = 20, M = 0.0, k = Flap oscillation, Expts
AR = 12, M = 0.2, k = 0.0, Heave, pitch
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17. Validation (Contd.) Static Aeroelasticity Dynamic 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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18. THANK YOU
4/15/2019