Spreading And Stability Analysis Of A Surfactant-laden Drop On Thermally Driven Thin Liquid Film

The spreading of surfactant solutions on the solid substrate or thin liquid films is an advancing topic of investigation with subject intersection. Such flows are of great importance in a wide range of coating, printing, oil production, paint and coatings industry, cosmetics, film production, magnetofluid preparation and surfactant replacement therapy.In the thesis, combining the methods of model derivation and numerical simulation, the spreading of surfactant drop on thin liquid film in presence of interfacial heating are investigated thoroughly and intensively. The main parts of the thesis are as following:(1) For the spreading of insoluble surfactant drop, for the film thickness and surfactant surface concentration equations for the base state and the corresponding contribution due to the perturbation are set. Each equation is evolved into five forms respectively for different heating conditions, uniform and non-uniform, on the condition of evaporation and no evaporation. The spreading of the drop and the effects of dimensionless parameters are investigated in details. Using numerical simulation and non-modal stability theory, through calculating the time-dependent relationship of the amplification ratios for the disturbances and overall instantaneous growth rates, the influence mechanism of surfactants properties and parameters on spreading stability are analyzed.(2) For the spreading of soluble surfactant drop, on the condition of evaporation and no evaporation and different heating, five groups equations for the film thickness and surfactant concentrations on the surface and in the bulk are set. The spreading of the drop and the effects of parameters are investigated in details, and the influence of them on stability is analyzed by the non-modal stability theory.