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

Flutter Analysis of the Polen Special II Emphasizing Addition of a Wet Wing and Ailerons to Flutter Model. Structural Engineers Erich Gross, Masayuki Wakamatsu Advisor: Marcus Kruger. ASE463Q [Fall2002] Final Presentation. Presentation Outline. Polen Special II Background and Specs

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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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  1. Flutter Analysis of the Polen Special IIEmphasizing Addition of a Wet Wing and Ailerons to Flutter Model Structural EngineersErich Gross, Masayuki Wakamatsu Advisor: Marcus Kruger ASE463Q [Fall2002] Final Presentation

  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. Outline • Polen & Project background • Flutter • AMAFALA • Results • 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

  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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Polen Special II Specifications • 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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclustion Past Polen Groups’ Works • 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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Project Objectives • 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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Dr. Ronald Stearman Consultant Department of Aerospace Engineering and Engineering Mechanics The University of Texas at Austin Javier Fuentealba AMAFALA Consultant Marcus Kruger Adviser Masayuki Wakamatsu Theoretical Research Past Group Data Analysis AMFAFALA Editing Erich Gross Team Leader Team Organization Past Group Data Analysis AMAFALA Editing Team Organization

  10. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Phenomena of Flutter (Flutter Theory) • 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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Flutter Video! Courtesy of www.airspacemag.com

  12. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Causes of Flutter (Flutter Theory) • 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…

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

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

  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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Wing Input File Overview • 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. Outline • Polen & Project background • Flutter • AMAFALA • Results • Conclusion Results: Case 1 (Original, Antisymmetric Condition) • No flutter occurrence is indicated for this condition

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

  22. Outline • Polen & Project background • Flutter • AMAFALA • Results • 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

  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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