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A ircraft D ynamic A nd ST atic A eroservoelastic A nalysis C ode Summary

A ircraft D ynamic A nd ST atic A eroservoelastic A nalysis C ode Summary P.M.Mujumdar, A. Joshi, K Sudhakar Aerospace Engineering, IIT Bombay. A ircraft D ynamic A nd ST atic A eroservoelastic A nalysis C ode. ADASTAAC ode. WHAT IS ADASTAAC.

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A ircraft D ynamic A nd ST atic A eroservoelastic A nalysis C ode Summary

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

  2. AircraftDynamicAnd STaticAeroservoelasticAnalysisCode

  3. ADASTAAC ode

  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)

  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

  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)

  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.

  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

  9. TIMELINE • 1992 – 1995 PHASE I • 1997 - 2001 PHASE II • Total work period = 3 + 4.5 = 7.5 years • Effort ≈ 12 man years • Total funds = 2 million Rs. • Code fully written by the team of 3 faculty members

  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

  11. Excluding LAPACK 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

  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)

  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.

  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

  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 • Mach no 0.0 to 2.0 • 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

  16. 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

  17. 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

  18. THANK YOU

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