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Influence of pitch rate on freely translating perching airfoils

Published online by Cambridge University Press:  20 June 2019

T. Jardin Open the ORCID record for T. Jardin [Opens in a new window]  and
N. Doué
T. Jardin*
Affiliation:
ISAE-SUPAERO, Université de Toulouse, 31055 Toulouse CEDEX 4, France
N. Doué
Affiliation:
ISAE-SUPAERO, Université de Toulouse, 31055 Toulouse CEDEX 4, France
*
†Email address for correspondence: [email protected]
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Abstract

We numerically investigated the unsteady dynamics of a two-dimensional airfoil undergoing a continuous, prescribed pitch-up motion and freely translating as a response to aerodynamic forces and the gravity field. The pitch-up motion was applied about an axis located $1/6$ chord away from the leading edge and was parameterized using the shape change number, with a Reynolds number set to 2000. It was shown that the minimum kinetic energy reached by the airfoil depends stochastically and asymptotically on shape change numbers for values below and above 1, respectively. Very low kinetic energy levels (close to zero) can be reached in both stochastic and asymptotic regions but high shape change numbers are accompanied by significant gain in altitude which may be undesirable from a practical perspective. Rather, shape change numbers in the range [0.1–0.3] allow us to reach relatively low levels of kinetic energy for close perching locations. We showed that highly nonlinear fluid–structure interactions induced by massive flow separations and strong vortices are conducive to low kinetic energy, but responsible for the stochastic dependence of kinetic energy to shape change number, which can make perching manoeuvres hardly controllable for flying vehicles.

JFM classification

Biological Fluid Dynamics: Swimming/flying
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 873 , 25 August 2019 , pp. 49 - 71
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Copyright
© 2019 Cambridge University Press 

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