Description
The yielding transition of soft glassy materials plays a crucial role in the flow and processing of complex fluids, including dense emulsions encountered in microfluidics and industrial applications. In this work, we investigate how asymmetric surface microroughness influences the flow of yield-stress emulsions through microchannels, with a focus on geometry-driven control of droplet and emulsion dynamics. We compare two engineered roughness geometries—herringbone riblets and wedge-shaped patterns—that introduce topological asymmetry along the flow direction. Experiments with yield-stress emulsions show that these patterns can enhance flow either in a directional way or selectively across the channel cross section: herringbone riblets induce pronounced flow banding with peak enhancement near the groove tips, while wedge-shaped ramps promote flow enhancement along the rising slope. Complementary numerical simulations using 2D Lattice Boltzmann methods highlight the interplay between pressure gradient, surface geometry, and non-Newtonian rheology in determining flow response. This combined experimental and computational study sheds light on how controlled surface design can modulate emulsion flow and droplet behavior under confinement, with potential implications for rheological control in microfluidic and industrial processes.