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An Experimental Study of Confinement Effects on Drop Coalescence via Hele-Shaw Cell
Drop coalescence is an interfacial fluid dynamics phenomenon in daily life. When an initial contact occurs between two drops, a liquid bridge is formed between them and rapidly grows. Eventually, the two drops merge to form a bigger drop. During the coalescence process, the evolution of the liquid bridge is driven by the surface tension existing between the drop and a surrounding medium. The resistance of drop coalescence is dominated by either the viscous or inertial force of the involved fluids. Since drop coalescence also occurs in various industrial processes, understanding the dynamics of drop coalescence under different conditions is crucial. Laboratory drop coalescence models have been used to study the dynamics of drop coalescence by recording and analyzing the temporal growth of the width or diameter of the liquid bridge. As a device composed of two parallel surfaces with a thin gap (i.e., much smaller gap width than the width of the device), the Hele-Shaw cell enables studying drop coalescence in narrow confinement, which is relevant to the coalescence of confined drops found in the aforementioned industry processes. However, only a few studies were conducted about the dynamics of drop coalescence in Hele-Shaw cells and the effect of the surrounding phase on drop coalescence. Regarding the effect of the confinement on drop coalescence, my study focused on the effects on the process of three-phase drop coalescence produced by the changing the gap width of the Hele-Shaw cell, and the effects on the process of two-phase drop coalescence produced by the highly viscous continuous phase in the Hele-Shaw cell. In three-phase drop coalescence studies, two scaling exponents describing the growth of the liquid bridge between the two drops were found at the early and the later stages of drop coalescence. It implies that the dynamics of drop coalescence are different from current studies. In two-phase drop coalescence studies, the effect of the confinement was diffused to DP through CP with high viscosity because of momentum diffusion.
Zhang, Haipeng, "An Experimental Study of Confinement Effects on Drop Coalescence via Hele-Shaw Cell" (2022). ETD collection for University of Nebraska - Lincoln. AAI29167698.