Flutter Analysis of the Polen Special II Emphasizing Addition of a Wet Wing and Ailerons to Flutter Model - PowerPoint PPT Presentation

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Flutter Analysis of the Polen Special II Emphasizing Addition of a Wet Wing and Ailerons to Flutter Model

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Title: Flutter Analysis of the Polen Special II Emphasizing in Adding Fuel Tank (and Aileron) Author: wakamam Last modified by: wakamam Created Date – PowerPoint PPT presentation

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Title: Flutter Analysis of the Polen Special II Emphasizing Addition of a Wet Wing and Ailerons to Flutter Model


1
Flutter Analysis of the Polen Special
II Emphasizing Addition of a Wet Wing and
Ailerons to Flutter Model
ASE463Q Fall2002 Final Presentation
  • Structural Engineers Erich Gross, Masayuki
    Wakamatsu
  • Advisor Marcus Kruger

2
Presentation Outline
  • Polen Special II Background and Specs
  • Project Motivation and Objectives
  • Past Polen Group Work
  • Flutter Theory
  • AMAFALA
  • Objectives Completed (Results)
  • Conclusions

3
Polen Special II Background
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Designed by Dennis Polen
  • Aluminum body, cantilevered low-wing,
    conventional
  • gear monoplane
  • Designed to achieve high speed (300mph)
  • Development began in 1967
  • First flew in 1972
  • Currently owned by Dick Keyt
  • Ex-Air Force, current American Airlines Pilot

4
Polen Special II Background
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Designed as a racing airplane
  • Mr. Keyt participates in various competitions
  • A longer range would be desirable
  • Wings are the only practical place to store
    additional fuel
  • Addition of wing fuel tanks was one of the
    primary project objectives

5
Polen Special II Specifications
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Polen Special II (Specifications courtesy of the
    EAA)
  • Model Year 1967
  • Engine Lycoming TSIO-360
  • Horsepower 180 hp normally aspirated, 200 hp
    turbocharged
  • Number of Seats 1
  • Length 19'6
  • Height 4'10
  • Wing Span 21'5
  • Gross Weight 1,500 lbs.
  • Max Speed 345 mph
  • Cruise Speed 325 mph
  • Service Ceiling 28,000 feet

6
Critical Problem and Project Motivation
Insufficient Flutter Analysis
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Rudder Damage

Courtesy of Spring 2001 463Q group
  • High frequency rudder flutter occurred during a
    low-pass fly-by
  • Fortunately, Mr. Keyt landed safely
  • Mr. Keyt requested a flutter analysis from the
    ASE department at UT Austin
  • Project has been developed since Fall 2000

7
Past Polen Groups Works
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclustion
  • Fall 2000 Spring 2001 (Not Accessible)
  • GVT, Modal Studies
  • Summer 2001
  • AMAFALA user manual initial input files
  • Fall 2001
  • Revision of input files wing tip EI and GJ
  • Spring 2002
  • Completed general Polen Models

8
Project Objectives
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Research flutter and analyze past data
  • Learn AMAFALA
  • Add components to the Polen model
  • Ailerons (Case 1)
  • Fuel Tanks Wet Wing
  • (Case 2, Case 3)

9
Team Organization
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion

10
Phenomena of Flutter (Flutter Theory)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Definition a self excited vibration of a
    flexible body ASE355 notes
  • Imagine a ball in these conditions
  •  

a) Stable
b) Neutral
c) Unstable
  • Flutter speed is defined as a minimum (neutral
    condition) speed at flutter occurs
  •  

11
Flutter Video!
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion

Courtesy of www.airspacemag.com
12
Causes of Flutter (Flutter Theory)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Inability of an airframe to dissipate energy to
    the airstreams
  • Airframeelastic deflects due to bending and
    torsion
  • New geometry - new aerodynamic force
  • And so on

13
To find the Flutter Speed
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Eigenvalue problems
  • i.e. seek the flutter speed and frequency
  • Structural Analysis and Aerodynamics
  • V-g Method

14
To find the Flutter Speed (V-g method)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion

g artificial structural damping (lt 0.033) Mach
number and altitude are held constant
  • V-g plot shows when flutter may occur
  • AMAFALA outputs a V-g plot

15
Flutter Symmetric VS Antisymmetric
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Two primary flutter conditions of interest
  • symmetric and antisymmetric

(a) symmetric
(b) Antisymmetric
  • For aileron flutter, we are concerned with the
  • antisymmetric case because ailerons are
    designed to
  • deflect antisymmetrically
  • We need to look at both symmetric and
    antisymmetric cases
  • to assess the changes caused by the new fuel
    tanks

16
AMAFALA (Airplane Modal Aerodynamic Flutter And
Loads Analysis)
  • A text-based flutter analysis program
  • Past 463Q teams worked with it
  • This is the main tool that we used in our
    analysis
  • Hard to learn- took two years for past groups to
    run the program
  • We modified existing input files created by
    Javier Fuentealba rather than creating new ones
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion

17
AMAFALA (Airplane Modal Aerodynamic Flutter And
Loads Analysis)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • AMAFALA Inputs
  • Geometric Data (layout of wing)
  • Mass Data (inertial strips)
  • Stiffness Data (inertial strips)
  • Aerodynamic Data
  • AMAFALA Outputs
  • Mode Frequencies
  • Mode Shapes
  • V-g Plots

18
Wing Input File Overview
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Input file contains geometric and mass data
    required to model the flutter characteristics of
    the wing
  • Original input file was complete except for the
    addition of ailerons and wing fuel tanks
  • We modified the original wing input file by
    adding the ailerons and fuel tanks to the wing

19
Wing Input File Overview
Visual Representation of Data Contained in Wing
Input File
New wing tanks
Aileron
Aileron CG
20
Results Case 1 (Original, Antisymmetric
Condition)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • No flutter occurrence is indicated for this
    condition

21
Results Case 1 (with Ailerons, Antisymmetric
Condition)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Flutter occurs at roughly 350 knots

22
Results Case 2 (New Fuel Tanks, Antisymmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks empty
  • Note This is identical to Case 1
  • Flutter occurs at roughly 350 knots

23
Results Case 2 (New Fuel Tanks, Antisymmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks half full
  • Flutter occurs at roughly 290 knots
  • 60 knots slower than for no additional tank case

24
Results Case 2 (New Fuel Tanks, Antisymmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks full
  • Flutter speed has fallen to 190-200 knots
  • Flutter is being induced!

25
Results Case 3 (Fuel, Symmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks empty
  • Flutter occurs at roughly 350 knots

26
Results Case 3 (Fuel, Symmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks half full
  • Flutter speed has fallen to 200 knots
    (conservative)
  • Realistically, flutter speed is probably closer
    to 275 knots

27
Results Case 3 (Fuel, Symmetric)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • New fuel tanks full
  • Flutter speed is now approximately 250-260 knots
  • Flutter speed is decreasing as fuel is added

28
Conclusions
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Case 1 aileron, antisymmetric
  • Flutter occurs at around 350 knots
  • Case 2 antisymmetric, new fuel tanks
  • Case 3 symmetric, new fuel tanks
  • Flutter speed decreases with the addition of
  • fuel to the new tanks
  • This is counterintuitive and undesirable
  • Centers of gravity for the new tanks must be
    moved closer to the wing leading edge
  • This will mean less fuel can be carried in the
    wing

29
Conclusion (Recommendations)
  • Outline
  • Polen Project background
  • Flutter
  • AMAFALA
  • Results
  • Conclusion
  • Learn AMAFALA ASAP
  • Develop more precise wet wing model
  • i.e, get more information about the structure
  • of the wing and edit wing file accordingly
  • Develop an external fuel tank mode

30
Questions?
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