Key Laboratory of Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, 100084 Beijing, China.
Key Laboratory of Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, 100084 Beijing, China.
J Colloid Interface Sci. 2019 Jul 1;547:87-91. doi: 10.1016/j.jcis.2019.03.091. Epub 2019 Mar 28.
Although the static flotation of elongated cylinders is well understood, their flotation behavior under dynamic conditions after contacting a liquid surface, such as in situations experienced by water-walking insects, still need to be revealed.
The motion of elongated horizontal cylinders after zero-velocity contact with a liquid surface is considered, and the motion equation of the cylinder is established and solved to obtain the dynamic flotation conditions.
The limiting density ratios for the dynamic flotation of elongated cylinders with different Bond numbers and contact angles are determined. The results show that although increasing the hydrophobicity promotes floatability of the elongated cylinders, there is little effect for contact angles >120°. Based on the energy balance, an asymptotic formula for the limiting density ratio is proposed, which agrees well with the theoretical results. Unlike small spheres, all elongated cylinders with contact angles >0° are observed to exhibit floatability after contacting a liquid surface. In addition, we found that elongated hydrophilic cylinders exhibit better floatability compared to small hydrophilic spheres with the same contact angle and Bond number, which assists small insects float and survive in various water environments.
尽管细长圆柱体的静态浮选已经得到很好的理解，但它们在接触液体表面后的动态条件下的浮选行为，如在水上行走昆虫所经历的情况，仍需要揭示。
考虑了水平细长圆柱体在与液体表面零速度接触后的运动，建立并求解了圆柱体的运动方程，以获得动态浮选条件。
确定了不同邦德数和接触角的细长圆柱体的动态浮选的极限密度比。结果表明，虽然增加疏水性会促进细长圆柱体的浮选性能，但接触角>120°时影响很小。基于能量平衡，提出了极限密度比的渐近公式，该公式与理论结果吻合较好。与小球体不同，所有接触角>0°的细长圆柱体在接触液体表面后都表现出浮选能力。此外，我们发现与具有相同接触角和邦德数的小亲水球体相比，亲水细长圆柱体表现出更好的浮选能力，这有助于小昆虫在各种水环境中漂浮和生存。
