Quasi-static secondary flow regions formed by microfluidic contraction flows of wormlike micellar solutions

This study investigates the effects of yield stress ( τ 0 ) and shear banding on the fluidic behaviors of cetyltrimethylammonium bromide/sodium salicylate wormlike micellar solutions flowing through a microfluidic planar contraction (8:1) geometry. Test solutions with different surfactant concentrations (Cd = 75, 87.5, and 100 mM) at a fixed molar ratio of salt to surfactant (R = 0.32) were characterized by shear and extensional rheometry. While the lower concentrated test solution (Cd = 75 mM) with low τ 0 (≈ 0.02 Pa) and no shear banding showed a Newtonian-like flow behavior for Mach number, Ma