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液体在润湿性微管中流动的边界负滑移特征

ISSN号：1000-4874
期刊名称：《水动力学研究与进展：A辑》
时间：0
分类：O351[理学—流体力学;理学—力学]
作者机构：[1]浙江海洋学院石油化工学院,浙江舟山316000, [2]浙江师范大学数理与信息工程学院,浙江金华321004
相关基金：国家自然科学基金项目（10972199,10932010）和国家重点基础研究发展计划（973计划,2013CB228000）

关键词：微尺度效应, 分子动力学, 润湿性, 滑移长度, 启动压力梯度, micro-scale effects, molecular dynamics, wettability, slip length, threshold pressure gradient

中文摘要：

该文通过分子动力学模拟,研究了亲水性壁面不同通道宽度中滑移长度的特征。结果表明在小剪切率下壁面存在负滑移,流体在固壁边界受到黏附力作用。在相同润湿性下,通道宽度不影响滑移长度,滑移长度只随壁面附近流体剪切率的变化而变化,滑移长度的绝对值随剪切率的增大而减小,当剪切率增大到某一值后滑移长度趋于定值。随后对去离子水在直径为10 m的亲水性微管内的流动进行了实验研究,并与分子动力学模拟结果进行了比较。实验结果表明：在低速流动下（剪切率较小时）,去离子水在微管内流动的流量与剪切率呈线性关系,且存在启动压力梯度,这是由于去离子水在微管内流动时的边界负滑移造成的,且滑移长度与剪切率呈非线性关系,随着剪切率的增大,实验值趋近于某一稳定值。这一实验结论与分子动力学模拟结果吻合的很好,表明了流体在润湿性微管内流动时,边界存在负滑移,固壁边界附近存在不流动的黏附层,这也是液体在低渗透多孔介质中渗流时存在启动压力梯度的原因。

英文摘要：

This paper presents the characteristics of slippage on the hydrophilic walls of different channel widths studied by molecular dynamics simulation. The simulation results indicate that there exists a reversal slip when shear rate small, and fluids on the wall are acted by adhesive force. At the condition of same wettability, the slip length is only related to shear rate of fluidsnear the wall rather than channel widths. The absolute value of slip length decreases with the augment of shear rate and keeps constant when the shear rate increases to a certain extent. Some experiments with deionized water flow through microtubes of 10 micrometer diameter were designed for experimental study and for validation with the simulation results. The experiment results show that there is a linear correlation between flow rate and the shear rate, and a threshold pressure gradient exists under the low speed flow. The existence reason of threshold pressure gradient is the affection of the reversal slip near the wall. The slip length is nonlinear with the shear rate. The nonlinearity gradually weakens and finally the result tends to a stable value with the increase of shear rate. The experiment results are in good agreement with the simulation results, which further illustrates that there are reversal slip and stagnant fluid layer near the solid wall boundary when fluid flow in the hydrophilic micro-tubes. This is why there exists threshold pressure gradient in low permeability porous media.

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