Dickinson, Michael H. and Götz, Karl G. (1996) The wake dynamics and flight forces of the fruit fly Drosophila melanogaster. Journal of Experimental Biology, 199 (9). pp. 2085-2104. ISSN 0022-0949 http://resolver.caltech.edu/CaltechAUTHORS:20120202-090257291
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We have used flow visualizations and instantaneous force measurements of tethered fruit flies (Drosophila melanogaster) to study the dynamics of force generation during flight. During each complete stroke cycle, the flies generate one single vortex loop consisting of vorticity shed during the downstroke and ventral flip. This gross pattern of wake structure in Drosophila is similar to those described for hovering birds and some other insects. The wake structure differed from those previously described, however, in that the vortex filaments shed during ventral stroke reversal did not fuse to complete a circular ring, but rather attached temporarily to the body to complete an inverted heart-shaped vortex loop. The attached ventral filaments of the loop subsequently slide along the length of the body and eventually fuse at the tip of the abdomen. We found no evidence for the shedding of wing-tip vorticity during the upstroke, and argue that this is due to an extreme form of the Wagner effect acting at that time. The flow visualizations predicted that maximum flight forces would be generated during the downstroke and ventral reversal, with little or no force generated during the upstroke. The instantaneous force measurements using laser-interferometry verified the periodic nature of force generation. Within each stroke cycle, there was one plateau of high force generation followed by a period of low force, which roughly correlated with the upstroke and downstroke periods. However, the fluctuations in force lagged behind their expected occurrence within the wing-stroke cycle by approximately 1 ms or one-fifth of the complete stroke cycle. This temporal discrepancy exceeds the range of expected inaccuracies and artifacts in the measurements, and we tentatively discuss the potential retarding effects within the underlying fluid mechanics.
|Additional Information:||© 1996 The Company of Biologists Limited. Accepted 20 May 1996. We wish to thank Michael Renner for his extensive help with the acquisition and processing of the flight force measurements. Fritz-Olaflehmann and Roland Strauss also provided additional technical support during the execution of this work. The authors would also like to thank the many helpful and provocative comments of two anonymous reviewers. This work was funded in part by the Max Planck Gesellschaft, the David and Lucille Packard Foundation and NSF Grant IBN-9208765 to M.H.D.|
|Subject Keywords:||vortex wake; insect flight; aerodynamics; Drosophila melanogaster|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||27 Feb 2012 18:25|
|Last Modified:||26 Dec 2012 14:46|
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