Microscopic flows of a simple yield stress material in the presence of wall slip

Eliane Younes (1) , Volfango Bertola (2) , Cathy Castelain (1) , Teodor Burghelea (1)

1 LTeN - Laboratoire de Thermique et d’Energie de Nantes
2 Department of Physics - University of Liverpool

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.

Mots clés: Carbopol gel; yield stress; rheology; microchannel; DPIV; wall slip

Domaines: Thermique [physics.class-ph]

Eliane Younes, Volfango Bertola, Cathy Castelain, Teodor Burghelea. Microscopic flows of a simple yield stress material in the presence of wall slip. Congrès Français de Mécanique CFM2019, Jun 2019, Brest, France. ⟨hal-02473040⟩