Zhang Ling-Zhe, Xu Sheng-Yao, Wang Yi-Feng, Yang Yan-Ru, Zheng Shao-Fei, Gao Shu-Rong, Wang Xiao-Dong, Lee Duu-Jong
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.
Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China.
Langmuir. 2022 Oct 4;38(39):11860-11872. doi: 10.1021/acs.langmuir.2c01271. Epub 2022 Sep 21.
This study numerically investigates the effects of the Weber number () and cylinder-to-droplet radius ratio () on the impact dynamics of a low-viscosity droplet on a hydrophobic cylinder by the lattice Boltzmann method. The intrinsic contact angle of the surface is chosen as = 122°± 2°, which ensures a representative hydrophobicity. The regime diagram of the impact dynamics in the parameter space of versus is established with categories of split and nonsplit regimes. The droplet would split during impact as α = / exceeds a critical value. In the nonsplit regime, the droplet bounces off the cylinder at most Weber numbers unless the impact velocity is minuscule ( < 2). The contact time of the droplet on the cylinder surface decreases with increasing or decreasing , indicating bouncing is facilitated under such conditions. This can be explained by the suppressed adhesion dissipation between the droplet and surface due to a reduction in the contact area. In the split regime, sufficient kinetic energy inside the impacting droplet determines whether the whole droplet could detach from the surface. With a small cylinder ( < 0.83) and large (>25), the adhesion effect is weakened for the side fragments because of the small contact area, and it facilitates the dripping of fragments. For other conditions, the detachment, especially for the tiny droplet on the cylinder top, only occurs if the deformation is prominent at > 35. Moreover, the spreading dynamics of the impacting droplet are also highlighted in this work.
本研究采用格子玻尔兹曼方法，数值研究了韦伯数（）和圆柱与液滴半径比（）对低粘度液滴在疏水圆柱上冲击动力学的影响。选择表面的固有接触角为 = 122°± 2°，以确保具有代表性的疏水性。在与的参数空间中建立了冲击动力学的状态图，包括分裂和不分裂状态类别。当α = /超过临界值时，液滴在冲击过程中会分裂。在不分裂状态下，除非冲击速度极小（< 2），液滴在大多数韦伯数下都会从圆柱上反弹。液滴在圆柱表面的接触时间随着的增加或的减小而减小，表明在这种条件下更容易反弹。这可以通过接触面积减小导致液滴与表面之间的粘附耗散受到抑制来解释。在分裂状态下，冲击液滴内部的足够动能决定了整个液滴是否能够从表面分离。对于小圆柱（< 0.83）和大（>25），由于接触面积小，侧面碎片的粘附效应减弱，这有利于碎片的滴落。对于其他条件，只有当变形在> 35时很突出时，分离才会发生，特别是对于圆柱顶部的微小液滴。此外，本研究还突出了冲击液滴的铺展动力学。
