Effect of Feather Elasticity of Kingfisher Wing on Droplet Impact Dynamics
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We experimentally studied droplet impact dynamics onto wing feathers of kingfishers. Distilled water droplets with a fixed diameter of 2.06 mm were used as drop liquid and the initial impact velocities of droplets varied from 0.28 m·s−1 to 1.60 m·s−1. Two high-speed cameras were utilized to capture the impact process of water droplets onto the wing feather surface from both horizontal and vertical directions. Two states of the feathers (elastic and inelastic) were considered to study the influence of elasticity. At the entire impact velocity range we studied, regular rebound, bubble trapping and jetting, partial pinning and partial rebound of droplets on inelastic wing feather surface were observed as the initial impact velocity increased. However, only one dynamic behavior (regular rebound) was found on the elastic wing feather surface. The elasticity plays a more important role in the direction difference of droplet spreading than wing feather microstructure. The contact time of water droplets on the elastic wing feather surface was less than that on the inelastic surface within the range of Web numbers from 1.06 to 36 under test conditions.
Keywordsbionic droplet impact kingfisher feather elasticity contact time spreading behavior
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This study was supported by the National Natural Science Foundation of China (Grant Nos. 51575227 and 51706084), the National Key Research and Development Program of China (Grant No. 2016YFE0132900), the Science and Technology Project of Jilin Provincial Education Department (Grant No. JJKH20170795KJ), and the Science and Technology Development Program of Jilin Province (Grant No. 172411GG010040701).
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