Very low Reynolds number causes a monotonic force enhancement trend for a three-dimensional hovering wing in ground effect

This research reports the numerical results of the ground effect trend for a three-dimensional
flapping insect wing at a very low Reynolds number (Re = 10). It demonstrates that the ground effect
trend at this Re has a ‘single force regime,’ i.e. the forces only enhance as the ground distance
decreases. This phenomenon is unlike the widely expected non-monotonic trend publicized in previous
studies for higher Reynolds numbers, that shows ‘three force regimes,’ i.e. the forces reduce,
recover, and also enhance as the ground distance decreases. The force trend in the ground effect
correlates to a similar trend in wing –wake interaction or the downwash strength on the wing’s head.
At very low Re (10), the very large viscosity causes diffused vortices and less advected vortex
wake, while at relatively high Re, the vortices are easily separated from the wing and then advected
downwards. This different development of the vortex wake caused different force trends for the
flapping wing i...

Source: Bioinspiration and Biomimetics - August 3, 2021 Category: Science Authors: Xueguang Meng, Anas Ghaffar, Yang Zhang and Chengjian Deng Source Type: research