In-Flight Wing-Membrane Strain Measurements on Bats
An efficient system for high-resolution measurements of a bat wing’s membrane during flight is presented, proving the feasibility of dynamic strain measurements on bats wing membranes during flapping. Data were collected from wind tunnel wind-off flights of a Jamaican fruit bat, Artibeus jamaicensis, a nocturnal and frugivorous specie trained by Brown University team to fly back and forth in the test section. Visual image correlation was used for image post-processing providing spatial highresolution three-dimensional displacements and strains on the bat’s wing.
Temporal membrane surface-averaged strain analysis showed a level of strain in the X direction (spanwise) approximately three times larger then the Y direction (chordwise) with values around 10% and 3%, respectively. Strains are estimated from an unknown reference state at the beginning of each recorded sequence. Full surface membrane strain distribution shows a consistent strain-relief effect around the ring finger during downstroke in the X direction (spanwise). Temporal wing section shape analysis during a down stroke revealed a higher camber and a significant pitch-up twist of the ring finger respect to the free membrane between the little and ring finger.
KeywordsWind Tunnel Test Section Ring Finger Wing Membrane Frugivorous Species
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