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

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

ADASTAAC ode 4/15/2019

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

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 4/15/2019

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) 4/15/2019

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. 4/15/2019

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 4/15/2019

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 4/15/2019

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

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 Excluding LAPACK 4/15/2019

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) 4/15/2019

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

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

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

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 4/15/2019

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 4/15/2019

THANK YOU 4/15/2019