The influence of time dependent flight and maneuver velocities and elastic or viscoelastic flexibilities on aerodynamic and stability derivatives

Alexander P. Cochrane, Craig G. Merrett, Harry H. Hilton

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The advent of new structural concepts employing composites in primary load carrying aerospace structures in UAVs, MAVs, Boeing 787s, Airbus A380s, etc., necessitates the inclusion of flexibility as well as viscoelasticity in static structural and aero-viscoelastic analyses. Differences and similarities between aeroelasticity and aero-viscoelasticity have been investigated in [2]. An investigation is undertaken as to the dependence and sensitivity of aerodynamic and stability derivatives to elastic and viscoelastic structural flexibility and as to time dependent flight and maneuver velocities. Longitudinal, lateral and directional stabilities are investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings one of the critical static parameters is the velocity at which control reversal takes place (VREVE). Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds VREV<≤VREVE, but furthermore does so in time at 0 < tREV ≤ ∞. The influence of the twin effects of viscoelastic and elastic materials and of variable flight velocities on longitudinal, lateral, directional and spin stabilities are also investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are here extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings the critical parameter is the velocity at which control reversal takes place (VREVE). Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds VREV<≤VREVE, but furthermore does so in time at 0 < tREV ≤ ∞. This paper reports on analytical analyses and simulations of the effects of flexibility and time dependent material properties (viscoelasticity) on aerodynamic derivatives and on lateral, longitudinal, directional and spin stability derivatives. Cases of both constant and variable flight and maneuver velocities are considered. Analytical results for maneuvers involving constant and time dependent rolling velocities are analyzed, discussed and evaluated. The relationships between rolling velocity p and aileron angular displacement β as well as control effectiveness are analyzed and discussed in detail for elastic and viscoelastic wings. Such analyses establish the roll effectiveness derivatives ∂[p(t)]V∞∂β(t). Similar studies involving other stability and aerodynamic derivatives are also undertaken. The influence of the twin effects of viscoelastic and elastic materials and of variable flight, rolling, pitching and yawing velocities on longitudinal, lateral and directional are also investigated. Variable flight velocities, encountered during maneuvers, render the usually linear problem at constant velocities into a nonlinear one.

Original languageEnglish (US)
Title of host publication10th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences, ICNPAA 2014
EditorsSeenith Sivasundaram
PublisherAmerican Institute of Physics Inc.
Pages403-412
Number of pages10
ISBN (Electronic)9780735412767
DOIs
StatePublished - Dec 10 2014
Event10th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences, ICNPAA 2014 - Narvik, Norway
Duration: Jul 15 2014Jul 18 2014

Publication series

NameAIP Conference Proceedings
Volume1637
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other10th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences, ICNPAA 2014
Country/TerritoryNorway
CityNarvik
Period7/15/147/18/14

Keywords

  • aero-viscoelasticity
  • aerodynamic derivatives
  • aileron effectiveness
  • control reversal
  • designer materials
  • stability derivatives
  • viscoelasticity

ASJC Scopus subject areas

  • General Physics and Astronomy

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