(454j) Understanding the Role of Vortex Recapture in Water Walking Insects Using a Mechanical Model and Computational Fluid Dynamics

Microvelia and Mesovelia are amongst many water-walking insects which locomote on both land and water using an alternate tripod gait. During their locomotion on water, these insects generate a pair of vortices during power strokes of their middle legs. Interestingly, in Microvelia, these vortices are captured and reenergized by the hind legs. However, this vortex recapture phenomenon was not observed in Mesovelia due to their long hind legs. Our objective of this study is to understand the role of vortex interactions with the hind legs in the locomotion of these insects on the water. We used high-speed imaging and particle imaging velocimetry (PIV) to study the kinematics and visualize the vortices shed from their legs. A mechanical model was built to systematically study the effect of the time difference between the strokes of two robotic arms and the stroke speed. Using computational fluid dynamics (CFD) modeling, we studied the interaction between the hind leg and the vortices shed from the middle leg to understand the forces involved in such interactions. We show that the vortices shed from the middle legs reduce the drag force on the hind legs. In this talk, we will also present our findings on the energetics of these insects during their locomotion on water. Overall, an in-depth understanding of the interfacial fluid dynamics involved in the locomotion of these insects may provide insights to improve the efficiency of water-walking microrobots.