1. Numerical Study of the Wall Slip Reduction Effects for a Double Concentric Cylinder Rheometer with Slotted Rotor
D. De Kee, Department of Chemical and Biomolecular Engineering, Tulane University
New Orleans, LA, 70118
The Computational Fluid Dynamics (CFD) method is used to numerically simulate the flow of a yield stress fluid in a double concentric cylinder rheometer with a slotted rotor (DCCR/SR). A modified Bingham model is used as the constitutive equation to describe a yield stress fluid. The wall slip boundary is modeled by the “slip-length” method. Figures (1a-d) illustrate that the stead-state flow curves measured by the DCCR/SR are numerically predicted with different wall slip conditions and compared to the curve predicted by the constitutive equation. The numerical results indicate that:
1) wall slip effects can be significantly reduced by opening slots on the rotor and
2) increasing the slot number or the slot ratio will further decrease wall slip effects.
Figure 1. Prediction of the apparent viscosity as a function of shear stress for different slot ratios S (defined as the ratio of the slot area to the entire rotor side surface area) and slot numbers N, according to the numerical simulation (symbols) and the theoretical model. (a) S = 0, N = 0; (b) S = 0.5, N = 18; (c) S = 0.7, N = 18; (d) S = 0.7, N = 72.