Closed‐end capillary rise—An experimental study

Abstract

The spontaneous rise of Newtonian liquids in closed-end capillaries is investigated with three different organics. Rise rate and equilibrium height are significantly reduced by a compression induced minor elevation in air pressure within the capillaries. We verify our earlier mathematical analysis quantifying viscous dissipation within air, and also show that the dynamic contact angle plays a material role. The relative importance of these varies with capillary dimensions. We also quantify the influence of atmospheric pressure variation and the temperature induced fluctuations in the rise height. A single parameter that relates static and dynamic contact angles is sufficient to match all of the data. This parameter is obtained from an open-capillary experiment. K E Y W O R D S closed capillary, compressible laminar flow, dynamic contact angle 1 | BACKGROUND Studies of single and multiphase flow in porous media rely upon an understanding of fluid dynamics and interface movement within capillaries. Applications include lab-on-a-chip and microfluidics, oil and gas production, drying, and so on. The dynamics of displacement, particularly with regard to the role of dynamic contact angle, is still an active research area. In open capillaries, modifications to Washburn equation due to inertia, dynamic contact angle, exit and entry losses, viscous dissipation in the gas phase vary in importance, depending on the dimensions of the capillary. 1 In closed capillaries however, inertia and losses play less of a role, and major corrections are due to dynamic

Molecular Dynamics Simulations of Lubricant Recycling in Porous Polyimide Retainers of Bearing

“…In such cases, in order to improve the prediction of the L–W function, the equilibrium contact angle should be replaced with a dynamic contact angle. The result has been confirmed by several studies using molecular dynamics simulations. , Researchers have proposed several dynamic contact angle models, which can be classified into four categories: hydrodynamic models, molecular kinetic models, molecular self-laying models, − and empirical models, among which the molecular self-laying models consider the existence of the precursor film and its effect on thin-film viscosity concerning the dynamic contact angle. At the microscopic scale, the precursor film affects the spreading rate of the liquid, which cannot be ignored during the determination of the contact angle; therefore, here, molecular self-laying models are used to describe the variation of the contact angle.…”