一维液态泡沫渗流实验研究及表面能和粘性耗散分析

液态泡沫由大量气泡密集堆积在微量表面活性剂溶液中形成，是远离平衡态的软物质. 泡沫强制渗流在微观上是指以恒定流率输入的液体在气泡间隙内的微流动过程，是影响泡沫稳定的主要因素之一. 采用在表面活性剂溶液中添加微量色素以显示泡沫中液体流动的方法，确定了透射率与液体分率的对应关系，测量得到了一维液态泡沫强制渗流中渗流波传播规律以及液体分率的演变规律；理论推导了泡沫基本单元，即开尔文单元结构(Kelvin cell)的粘性耗散能表达式，并依据Surface Evolver软件计算得到了不同液体分率时开尔文单元结构对应的的表面能，并计算出了与实验系统对应的开尔文单元结构的表面能和粘性耗散. 基于开尔文单元结构内液体分率演变的准静态假设，分析了表面能和粘性耗散的演变规律.

Experimental study and analysis of energy evolution of liquid foam drainage in one dimension

Liquid foam is a dense packing of gas bubbles in a small amount of surfactant liquid, which has well-organized structure and behaves as typical soft condensed matter. Forced drainage is the flow of constantly input liquid through the network of interstitial channels between bubbles in foams under actions of gravity and capillarity, which is one of major mechanisms causing liquid foam evolution. Firstly in this paper, we improved the newly proposed method introduced by Hutzler et al. (2005) by considering the light transmission ratio to eliminate the incident light intensity discrepancy along the one dimensional foam formed within a slender Hele-Shaw silicon rectangular tube. After the film rupture and the bubble coarsening were carefully slowed down, forced foam drainages in one dimension were studied by using the improved light scattering technique. We found that the characteristic quantities, such as the drainage wave front velocity and liquid fraction evolution, are consistent with traditional foam drainage results based on Poiseuille-type flow assumption in Plateau borders. And the light transmission ratio is found not to be the reciprocal of the liquid fraction as similar with the transmission probability in diffuse-transmission spectroscopy technique, but prevails the relationship T=0.293+1.038e^-29.39(0.01<<0.13). We then deduced the viscous energy of foams based on Kelvin cell structure during forced drainage process and calculated the surface energy of foam using the software of Surface Evolver. The evolution of the two kinds of energy at local area of foam was predicted based on the quasi-static assumption of Kelvin cell structure evolution along with liquid fraction variation. The study of foam drainage from a view of energy will be useful in the further study on foam drainage and foam stability control in various applications.