非平整基底上活性剂驱动的液滴铺展稳定性研究  

Study on stability of surfactant-driven droplet spreading overt opographic substrate

作　　者：李春曦[1,2,3] 苏浩哲 童嘉铭 叶学民 Chunxi LI;Haozhe SU;Jiaming TONG;Xuemin YE(Department of Power Engineering,North China Electric Power University,Baoding,Hebei 071003,China;Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology,North China,Electric Power University,Baoding,Hebei 071003,China;Baoding Key Laboratory of Low Carbon and High Efficiency Power Generation Technology,North China Electric Power University,Baoding,Hebei 071003,China)

机构地区：[1]华北电力大学动力工程系,河北保定071003 [2]华北电力大学河北省低碳高效发电技术重点实验室,河北保定071003 [3]华北电力大学保定市低碳高效发电技术重点实验室,河北保定071003

出　　处：《过程工程学报》2022年第8期1019-1029,共11页The Chinese Journal of Process Engineering

基　　金：国家自然科学基金资助项目(编号:5187605)。

摘　　要：当含有表面活性剂的液滴放置在液膜上时,受表面张力梯度的驱动,液滴会自发向外铺展。在铺展过程中,初始微小扰动会在非线性作用的影响下产生以指进现象为特征的不稳定现象,并与基底几何特征密切相关。基于润滑理论推导的液膜厚度和活性剂浓度演化方程,采用FreeFEM++语言编写数值模拟程序,应用微软MS-MPI运行库进行并行化处理,模拟了非平整基底对含活性剂液滴铺展过程中指进现象的影响,使用功率谱方法分析了不同波数对应的扰动能量增长规律,探究了Marangoni效应、毛细效应与扰动能量间的变化关系,揭露了非平整基底对不稳定性的影响机理。结果表明,非平整基底对手指形貌影响不大,但对手指下游影响明显;不同波数对应的扰动能量存在不同的演化特征,优势波数为20和7;最大扰动能量出现在初始条件设置扰动处,与平整基底相对比,凹槽基底可抑制扰动发展,总扰动能量约为平整基底的80%;波纹基底可促进扰动发展,总扰动能量约为平整基底的105%,且波纹基底在初期对特定波数的扰动有明显的促进作用。总体地,非平整基底通过改变活性剂浓度分布影响扰动能量,进而影响指进现象。When a droplet laden with surfactant landing on a thin film, spontaneous spreading driven by surface-tension gradient occurs. Affected by the non-linear impact, the initial small disturbances lead to an unstable fingering phenomenon during the spreading, which is closely related to the topographic substrates. Based on the evolution equations of liquid film height and surfactant concentration derived from the lubrication approximation, FreeFEM++ is employed for simulation coding, and the Microsoft MS-MPI runtime library is applied for parallel computing. The influence of the topographic substrates on the instability is examined, the power spectrum is employed to analyze the growth law of disturbance energy corresponding to different wavenumbers, the relation between the Marangoni effect, the capillary effect, and the disturbance energy is investigated, as well as the internal mechanism of the topographic substrate on instability is explored. The results show that the topographic substrates deal little influence on the fingers, but a lot on the region downstream.Disturbance energy with different wavenumbers present different evolution characteristics, and the dominant wavenumbers in this study are 20 and 7. On the notch base, wavenumbers selected from random disturbance is consistent with transient growth analysis(TGA), which means that notch base does not change the wavelength select mechanism. The maximum disturbance energy appears at the position setting the initial condition. Compared with the flat base, the notch base can inhibit the development of disturbances, and the total disturbance energy is reduced to approximately 80%. Whereas the corrugated base can promote the development of disturbances, and the total disturbance energy is increased to about 105%, and the corrugated base has a strong promotion on the disturbances corresponding to specific wavenumbers in the initial stage, which is consistent with TGA. In general, the topographic substrate affects the disturbance energy by changing the concentration

关 键 词：活性剂铺展 MARANGONI效应 润滑理论 指进现象 并行计算 

分 类 号：O552.4[理学—热学与物质分子运动论]