Uncoupling the effects of aspect ratio, Reynolds number and Rossby number on insect wings

What is it about?

Aspect ratio, Reynolds number and Rossby number are the three important parameters affecting the insect wing aerodynamics. Past studies, typically of the aspect ratio, show conflicting trends in the effects on the wing aerodynamics. This study presents an investigation of the combined and individual effects of these three parameters over a wide range of values relevant to most insects. Based on this study, and a previous study from our group, the Reynolds number and Rossby number are redefined using the wingspan as the length scale. The apparently conflicting trends in past studies are shown to be reconciled with the proposed definitions. Moreover, this study also provides physical insights into the optimum range of aspect ratios observed at different flying speeds in nature.

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Why is it important?

Our findings show that the wingspan is a more appropriate length scale for rotating and flapping wings than the traditional length scale of the wing chord. Accordingly, the modified scaling of Reynolds number and Rossby number help reconcile conflicting past studies. The new definitions will also help understand the flow over insect wings better in a wide range of future studies.

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