表面活性剂浓度对球形气泡界面和尾流的影响

发展了一种研究气泡界面污染程度的数值模型,并用其对流场中不同表面活性剂浓度下、上浮气泡的界面参量和周围流场进行了模拟研究。该模型假设吸附于气泡界面的表面活性剂分布在毗邻气液界面的薄吸附层中,且气泡界面上表面活性剂的吸附与解吸过程也发生于此;界面切应力为界面浓度的函数。研究发现:气泡界面的流动性会因表面活性剂的吸附而降低,该现象会增大气泡周围流域中切向速度在界面法向上的变化量,从而对界面性质和周围流场产生影响;由于对流的作用和吸附-解吸动态平衡的存在,气泡前部界面不完全干净,且受污染界面的流动性也不完全为零。

Effects of Surfactant Concentration on Interfacial and Wake Properties of a Spherical Bubble

The numerical model is improved to study the hydrodynamics of a contaminated bubble.Based on the developed method,the interfacial parameters and the surrounding flow field of a rising bubble are numerically investigated under different bulk concentrations of surfactants.The surfactant adsorbed on the bubble surface is modeled by submerging them in the thin adsorption layer adhered on the bubble.The processes of adsorption and desorption at the interface are also assumed to be taken place there.The inherent tangential stress on the bubble surface is evaluated via its combination to the interfacial concentration of surfactants.It is found that the adsorption of surfactants retards the interface.Then,the gradient of tangential velocity is thus induced near the bubble perpendicular to its surface.This phenomenon further affects the interfacial properties of the bubble and the flow field around it.The front interface is not purely clean while the rear contaminated interface is not completely retarded due to the convection effect and the dynamic balance of adsorption and desorption on the bubble surface.