MAE Distinguished Speaker Series 2026 Seminar on At the Edge of Contact-Motion Interface

Professor Q. Jane Wang

Joseph Cummings Professor in Mechanical Engineering

Northwestern University, United States

This seminar will be chaired by Asst Prof Song Binyang.

When two surfaces are in a flooded wedged contact and relative motion, how does the fluid boundary layer behave? Blocked wedge flow driven by a moving surface poses a uniquely complex scenario as there is no physical gap for flow to exit the channel. It challenges the Reynolds equation and other computational fluid dynamics (CFD) theories with failure to capture the true fluid-solid interfacial status, which is neither no-slip, nor slip. Fluid flow is repelled backwards, being brought to a stop or reversing flow, which generates a variable slip condition at the fluid-solid interface. We investigated this problem via novel molecular dynamics (MD) modeling of fluid argon, as discrete particles, flowing towards the tip of a fully blocked convergent channel. Boundary layer velocities were captured to characterize the behavior of the boundary layer and the evolution of flow profiles and stresses approaching the blocked convergent gap subjected to relative motion. The simulation has resulted in a set of formulas describing the true slip condition with respect to the steepness of wedged channel, interatomic forces, fluid particle size, and molecular structure. Ongoing work aims to explore the connection of the new interfacial physics with CFD, renewal of mixed-lubrication theories, and impact of the results on micro-nano-fluidic designs. Recent research progress on multifield contact and lubrication theories will also be discussed.