Microscopic flows of a simple yield stress material in the presence of wall slip
Résumé
A fundamental problem in the hydrodynamics of yield stress fluids relates to the "wall slip" phenomenon. To tackle this, we have performed systematic measurements of flow fields of a simple yield stress fluid (Carbopol Ultrez 10) in a plane acrylic made micro-channel. By means of epifluorescent microscopy combined with a customly developed Digital Particle Image Velocimetry, times series of velocity fields were measured within a wide range of driving flow rates and three distinct flow regimes were identified: full plug, partial plug and fully yielded. Corresponding to each flow regime, the wall velocity gradients and slip velocities are obtained by interpolating the velocity profiles using a smoothing spline function. Furthermore, by combining the flow field measurements with the macro-rheological measurements of the flow curves, we identify scaling laws of the slip velocity with the wall shear stress. Finally, we present a detailed comparison of the experimentally found scaling laws of the wall slip with results from the literature.
Domaines
Thermique [physics.class-ph]Origine | Fichiers produits par l'(les) auteur(s) |
---|