Inertial effects on flow dynamics near a moving contact line

TL;DR

This paper explores how inertia influences flow near moving contact lines through experiments, theory, and simulations, revealing inertia causes systematic deviations in flow patterns at moderate Reynolds numbers.

Contribution

It extends existing models by analyzing inertial effects on contact line flow, highlighting limitations of current theories at higher Reynolds numbers.

Findings

Inertia causes measurable deviations in flow contours at Re > 0.1.

Inertial-MWS theory matches experiments only within Re 0.1 to 1.

Simulations confirm experimental deviations and show interfacial speed decay at finite Re.

Abstract

This study investigates the role of inertia in moving contact lines using experiments, theoretical analysis, and numerical simulations. Experiments are conducted using a plate immersion configuration over a wide range of Reynolds numbers from $O(10^{-3})$ to $O(10)$. Flow configurations and quantitative measurements are obtained using high-speed imaging and particle image velocimetry. The streamfunction contours reconstructed from the experimental velocity fields are compared with the viscous modulated wedge solution (viscous-MWS) and inertial-MWS theory. Experimental observations show that the streamfunction contours agree well with viscous predictions at low Reynolds numbers; however, systematic deviations emerge as the Reynolds number increases. The inertial-MWS theory, an inertial extension of the Huh and Scriven framework, accounts for these deviations, but only within a narrow range of Reynolds numbers $10^{-1} < Re < 1$. At higher Reynolds numbers, inertial theory fails to accurately capture the deviations in the streamfunction contours observed in the experiments. Moreover, simulations conducted using the volume of fluid method support our findings, exhibiting deviations in streamfunction contours consistent with experimental observations. We demonstrate that inertia does not fundamentally alter the underlying flow configuration but instead induces a systematic deviation in the streamfunction contours. At finite $Re$, the interfacial speed transitions from a nearly constant value in the viscous regime to a monotonic decay along the interface. These findings expose the need for more sophisticated models of moving contact lines.