Sharif Digital Repository

Individual drops are suitable tools to study the liquid-fluid interfacial properties. In this work, force-displacement equation and non-linear oscillations of a pendent drop are numerically investigated. The presented novel force-displacement function allows following the dynamics of a pendent drop and realizing its elastic behavior. The growth and detachment of drop, which is pending due to gravity from a capillary tip, is considered (assuming high density and high viscosity ratios and immiscible two-phase flows). Two-dimensional multi-relaxation time lattice Boltzmann method (MRT-LBM) was used to simulate growth, detachment, and oscillations of the drop using a conservative model for... 

Dynamic interfacial parameters are the key properties of interfaces in many modern technologies and can be studied in various ways. For applications like foams and emulsions, the dynamics of adsorption and the dilational and shear rheology of liquid-fluid interfaces are investigated most frequently. This work gives an insight into recently developed new experimental approaches, such as fast capillary pressure tensiometry for growing and oscillating drops. These experiments are presented in comparison to more classical techniques like drop profile tensiometry and capillary wave damping. Progress in these experiments based on generated interfacial perturbations can be expected only by a close... 

Capillary pressure experiments were performed at the water/hexane interface including adsorption and mass exchange of hexanol under different conditions. The results from growing drop experiments show that instabilities due to Marangoni convection not only depend on the same parameters as have been reported for quasi-static interfaces, such as direction of mass transfer, distribution coefficient and ratio of diffusion coefficients, but also on the experimental conditions such as dispersed phase flow rate, capillary tip size, size of growing drop and its lifetime. Based on a new flow expansion model for mass transfer, a new approach is presented for data analysis, which includes the various... 

Profile analysis tensiometry (PAT) is presently the most frequently used technique for measuring surface tensions of liquids. The basis of this methodology is however an equilibrium force balance as given by the Gauss-Laplace equation. Therefore, its application under dynamic conditions, i.e. for growing drops or bubbles, is questionable. We discuss the limits of the applicability of PAT under dynamic conditions by using a growing drop configuration equipped with a high speed video camera. The systems studied are the water/air and water/hexane interface. The obtained "dynamic" drop profiles are analyzed by fitting the classical Gauss-Laplace equation. The results are additionally compared...