Moving contact lines and Langevin formalism
Moving contact lines and Langevin formalism
复制标题
DOI：
10.1016/j.jcis.2019.11.123
复制
发表时间：
2020-03-07
影响因子：
9.9
通讯作者：
De Coninck, J.
中科院分区：
文献类型：
--
作者：
Fernandez-Toledano, J-C;Blake, T. D.;De Coninck, J.
假设：在以前的工作[J. - C. Fernando-Toledano，T.D. Blake”J. De Coninck，J. Colloid Interface Sci. 540（2019）322-329]，** 我们使用分子动力学（MD）来表明，在平衡时在液体和固体之间形成的接触线的热振荡可以用过阻尼的1-D朗之万谐振子来解释。的方差的接触线的位置和阻尼率的自相关函数，使我们能够确定接触线的摩擦系数zeta，从而预测润湿的动力学。我们现在提出，同样的方法可以应用到一个移动的接触line.Methods：我们使用相同的MD系统，如前所述，两个固体板之间形成的液体桥，但现在我们移动板在一个稳定的速度U-板在相反的方向产生前进和后退的接触线和它们相关的动态接触角θ（d）。然后记录并分析一系列板速度和固液相互作用的接触线位置和动态接触角的波动。我们证实，波动的移动接触线也可以解释在1-D谐振子，并推导出一个朗之万表达式类似于所获得的平衡的情况下，但是谐波项以动态接触线x（d）的平均位置为中心，而不是以其平衡位置x（θ）为中心，并且波动毛细力由动态接触角在θ（d）附近而不是平衡角θ（θ）的波动引起。我们还确认了在被认为是L-y的接触线的长度上的波动的方差、振荡的时间衰减和摩擦力zeta之间的直接关系。此外，我们证明了一个新的关系，我们的系统之间的距离平衡x（d）-x（0）和脱离平衡的毛细作用力γ（L）（cos θ（0）- cos θ（d）），其中γ（L）是液体的表面张力，并表明，无论是波动的方差和它们的时间衰减依赖于U板。我们的分析产生的zeta值几乎相同的扩散液滴的模拟确认的共同性质的耗散机制在接触线。(C)2019爱思唯尔公司All rights reserved.
Hypothesis: In previous work [J.-C. Fernandez-Toledano, T.D. Blake" J. De Coninck, J. Colloid Interface Sci. 540 (2019) 322-329], **we used molecular dynamics (MD) to show that the thermal oscillations of a contact line formed between a liquid and a solid at equilibrium may be interpreted in terms of an overdamped 1-D Langevin harmonic oscillator. The variance of the contact-line position and the rate of damping of its self-correlation function enabled us to determine the coefficient of contact-line friction zeta and so predict the dynamics of wetting. We now propose that the same approach may be applied to a moving contact line.Methods: We use the same MD system as before, a liquid bridge formed between two solid plates, but now we move the plates at a steady velocity U-plate in opposite directions to generate advancing and receding contact lines and their associated dynamic contact angles theta(d). The fluctuations of the contact-line positions and the dynamic contact angles are then recorded and analyzed for a range of plate velocities and solid-liquid interaction.Findings: We confirm that the fluctuations of a moving contact line may also be interpreted in terms of a 1-D harmonic oscillator and derive a Langevin expression analogous to that obtained for the equilibrium case, but with the harmonic term centered about the mean location of the dynamic contact line x(d), rather than its equilibrium position x(0), and a fluctuating capillary force arising from the fluctuations of the dynamic contact angle around theta(d), rather than the equilibrium angle theta(0). We also confirm a direct relationship between the variance of the fluctuations over the length of contact line considered L-y, the time decay of the oscillations, and the friction zeta. In addition, we demonstrate a new relationship for our systems between the distance to equilibrium x(d)-x(0) and the out of equilibrium capillary force gamma(L) (cos theta(0) - cos theta(d)), where gamma(L) is the surface tension of the liquid, and show that neither the variance of the fluctuations nor their time decay depend on U-plate. Our analysis yields values of zeta nearly identical to those obtained for simulations of spreading drops confirming the common nature of the dissipation mechanism at the contact line. (C) 2019 Elsevier Inc. All rights reserved.