论文标题
接触角滞后可以调节牛顿杆攀爬效果
Contact angle hysteresis can modulate the Newtonian rod climbing effect
论文作者
论文摘要
本工作使用实验和数值方法研究了接触角滞后在液体液固体界面（LLS）对两种不混溶的牛顿液体的杆攀爬效果上的作用。实验表明，在LLS接口处的最终稳态接触角，$θ_{w} $随杆旋转速度（$ω$）而变化。对于当前系统，$θ_{w} $从$ \ sim $ 69 $^{\ circ} $更改为$ \ sim $ 83 $^{\ circ} $，当杆的状态从静态条件更改为3.3 Hz旋转。随着$ω$的进一步增加，$θ_{w} $超过90 $^{\ circ} $，这是无法通过实验观察到的。从模拟中推断出的输入值$θ_{w} $饱和，并达到$ \ sim $ 120 $^{\ circ} $的常数值为$ω> $ 5 hz。使用数值模拟，我们证明必须考虑这种接触角滞后，以正确预测牛顿杆攀爬效果。使用在边界条件下接触角的适当值，可以根据以下方式获得实验和模拟之间的极好的定量匹配：攀爬高度，攀登发作的阈值杆旋转速度以及液体液体界面的形状。这可以解决现有文献中实验和模拟之间的差异，在现有文献中，接触角的恒定值已用于杆旋转的所有速度。
The present work investigates the role of contact angle hysteresis at the liquid-liquid-solid interface (LLS) on the rod climbing effect of two immiscible Newtonian liquids using experimental and numerical approaches. Experiments revealed that the final steady state contact angle, $θ_{w}$ at the LLS interface varies with the rod rotation speed, $ω$. For the present system, $θ_{w}$ changes from $\sim$69$^{\circ}$ to $\sim$83$^{\circ}$ when the state of the rod is changed from static condition to rotating at 3.3 Hz. With further increase in $ω$, the $θ_{w}$ exceeds 90$^{\circ}$ which cannot be observed experimentally. It is inferred from the simulations that the input value of $θ_{w}$ saturates and attains a constant value of $\sim$120$^{\circ}$ for $ω>$ 5 Hz. Using numerical simulations, we demonstrate that this contact angle hysteresis must be considered for the correct prediction of the Newtonian rod climbing effect. Using the appropriate values of the contact angle in the boundary condition, an excellent quantitative match between the experiments and simulations is obtained in terms of: the climbing height, the threshold rod rotation speed for onset of climbing, and the shape of liquid-liquid interface. This resolves the discrepancy between the experiments and simulations in the existing literature where a constant value of the contact angle has been used for all speeds of rod rotation.
