分离压对不同基底上含活性剂液滴铺展特征的影响

Effect of Disjoining Pressure on Spreading of Droplet Containing Surfactant over Different Topography Surfaces

针对不同基底结构上含不溶性活性剂液滴的铺展过程,引入受活性剂浓度影响的分离压模型,应用润滑理论建立了液滴厚度和活性剂浓度演化方程组,通过数值计算得到了分离压作用下含活性剂液滴过程的演化特征。研究表明不考虑分离压时,最小液膜高度贴近壁面,诱发去润湿现象发生,基底不平整度增加加剧液膜变形;分离压作用下最小液膜高度显著上升,铺展前沿处衍生出的子波结构明显减少,铺展更加稳定;分离压具有抑制液膜表面变形促进液滴铺展的作用。

Considering the spreading process of an insoluble surfactant-laden droplet over topography with different structures, this paper introduces a disjoining pressure model induced by the concentration of the surfactant. The lubrication theory is applied to derive the evolution equations of droplet thickness and interfacial surfactant concentration. And the characteristics of the droplet spreading process under disjoining pressure are numerically simulated. The results indicate that without the regard of the effects of the disjoining pressure, the minimum height of film is close to the wall which leads to wetting phenomenon; the increase of the substrate roughness can exacerbate film deformation; under the effects of the disjoining pressure, the minimum height of film tends to rise significantly; at the advancing front of the droplet, the number of wavelet tends to decrease obviously, which improves the stability of spreading. In addition, the disjoining pressure can inhibit the film surface deformation and promote the droplet spreading.