Welcome to the final lecture in the PoreLab Lecture Series for the semester!
Who: Dr. Bauyrzhan Primkulov, from the Massachusetts Institute of Technology, USA
When: Wednesday 7 June at 13:00 (Oslo time)
Title: Moving contact lines over imperfect surfaces: from stick-slip to steady-sliding
The vast majority of solid surfaces exhibit physical and chemical defects. For instance, surface heterogeneity of a window glass is apparent in how it interacts with rain—here, larger raindrops slide smoothly down the slope, smaller ones remain pinned, and droplets of intermediate size undergo macroscopic stick-slip motion. The complex behavior of fluid-fluid interfaces moving over heterogeneous solid surfaces has captivated the fluid-mechanics community over the past several decades, driven by the elegant physics of the problem and the multitude of relevant practical applications. Here, we reduce the dynamics of fluid-fluid displacement in partial wetting to a system of coupled ordinary differential equations. This allows reducing the complexity of stick-slip dynamics to a few key parameters, elucidating both constant-force and constant-rate displacement regimes through a mechanical analog. We demonstrate that stick-slip motion crosses over to steady sliding at high displacement rates, revealing a balance of timescales that helps rationalize observations of stick-slip dynamics in recent experimental studies.