Transcript Flutter Analysis of the Polen Special II Emphasizing in

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
Presentation Outline
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Polen Special II Background and Specs
Project Motivation and Objectives
Past Polen Group Work
Flutter Theory
AMAFALA
Objectives Completed (Results)
Conclusions
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Polen Special II Background
 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
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Polen Special II Background
 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
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Polen Special II Specifications
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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
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Critical Problem and Project Motivation:
Insufficient Flutter Analysis
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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
Past Polen Groups’ Works
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclustion
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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
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Project Objectives
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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)
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Team Organization
Dr. Ronald Stearman
Consultant
Department of Aerospace Engineering
and Engineering Mechanics
The University of Texas at Austin
Marcus Kruger
Adviser
Javier
Fuentealba
AMAFALA
Consultant
Masayuki
Wakamatsu
Theoretical Research
Past Group Data Analysis
AMFAFALA Editing
Erich Gross
Team Leader
Team Organization
Past Group Data Analysis
AMAFALA Editing
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Phenomena of Flutter (Flutter Theory)
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Definition: a self excited vibration of a flexible
body [ASE355 notes]
Imagine a ball in these conditions
a) Stable
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b) Neutral
c) Unstable
Flutter speed is defined as a minimum (neutral
condition) speed at flutter occurs
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Courtesy of www.airspacemag.com
Flutter Video!
Causes of Flutter (Flutter Theory)
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
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Inability of an airframe to dissipate energy
to the airstreams
 Airframe—elastic; deflects due to
bending and torsion
 New geometry - new aerodynamic force
 And so on…
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
To find the Flutter Speed
Eigenvalue problems
 i.e. seek the flutter speed and frequency
 Structural Analysis and Aerodynamics
 V-g Method
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To find the Flutter Speed (V-g method)
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
g: artificial structural
damping (< 0.033)
Mach number and altitude
are held constant
V-g plot shows when flutter may occur
AMAFALA outputs a V-g plot
Flutter: Symmetric VS Antisymmetric
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
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
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
Outline
Hard to learn- took two years for past groups to
1)
Polen &
run the program
Project
background
We modified existing input files created by
2)
Flutter
3)
AMAFALA
Javier Fuentealba rather than creating new ones
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4)
Results
5)
Conclusion
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
AMAFALA (Airplane Modal Aerodynamic
Flutter And Loads Analysis)
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
Wing Input File Overview
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
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Input file contains geometric and mass data
required to model the flutter characteristics of the
wing
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Original input file was complete except for the
addition of ailerons and wing fuel tanks
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We modified the original wing input file by adding
the ailerons and fuel tanks to the wing
Wing Input File Overview
Visual Representation of Data Contained in Wing Input File
New wing tanks
Aileron
Aileron CG
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 1 (Original, Antisymmetric Condition)
No flutter occurrence is indicated for this condition
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 1 (with Ailerons, Antisymmetric Condition)
Flutter occurs at roughly 350 knots
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 2 (New Fuel Tanks, Antisymmetric)
New fuel tanks empty
Note: This is identical to Case 1
Flutter occurs at roughly 350 knots
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 2 (New Fuel Tanks, Antisymmetric)
New fuel tanks half full
Flutter occurs at roughly 290 knots
60 knots slower than for no additional tank case
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 2 (New Fuel Tanks, Antisymmetric)
New fuel tanks full
Flutter speed has fallen to 190-200 knots
Flutter is being induced!
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 3 (Fuel, Symmetric)
New fuel tanks empty
Flutter occurs at roughly 350 knots
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 3 (Fuel, Symmetric)
New fuel tanks half full
Flutter speed has fallen to 200 knots (conservative)
Realistically, flutter speed is probably closer to 275 knots
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Results: Case 3 (Fuel, Symmetric)
New fuel tanks full
Flutter speed is now approximately 250-260 knots
Flutter speed is decreasing as fuel is added
Conclusions
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Case 1 [aileron, antisymmetric]
 Flutter occurs at around 350 knots
 Case 2 [antisymmetric, new fuel tanks]
 Case 3 [symmetric, new fuel tanks]
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 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
Conclusion (Recommendations)
Outline
1)
Polen &
Project
background
2)
Flutter
3)
AMAFALA
4)
Results
5)
Conclusion
Learn AMAFALA ASAP
 Develop more precise wet wing model
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 i.e,
get more information about the structure
of the wing and edit wing file accordingly
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Develop an external fuel tank mode
Questions?