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Visualisation of hairpin vortex packets in the near-ground atmospheric boundary layer during daytime

Cho, Moonsung

Visualisation of the flow structure near the ground is important to understand aerial locomotion of a passive flying animal. The video shows the visualized structures of several hairpin vortex packets in the near ground atmospheric boundary layer during daytime. The hairpin vortex packets appear as a wedge-like shape. The structure develops upwards, as it drifts in the downwind direction. (Mean wind speed: 1.96 m/s at 0.95 m above the ground) These packet structures can be used by passive flyers, such as spiders, for their aerial dispersal during their take-off phase. The image processing technique has been applied. The faint smokes are recognized by comparing the RGB vectors with that of the background and amplified. The recognized smokes are negatively visualized as the color of white.