Sensitivity Study of Bingham Fluid Flow by the Ratio of Inner and Outer Diameters of Annulus

As for flow of drilling fluids, typically for laminar flow and friction of Bingham plastic fluid, in a concentrate annulus, direct numerical simulations (DNS) are carried out and compared with MR (Metzner Reed, MR) approximate solutions. As the sensitivity research parameter of present paper, the ratio of inner and outer diameter of annulus is prescribed to be 0.3, 0.5, 0.7 and 0.9. As such ratio decreases, the difference between velocity profiles obtained by DNS and MR approximate solutions keeps increasing; compared with DNS, ranges of flow cores via MR approximate solutions are varied from narrow to wide; differences between two maximal velocities also gradually increase, even up to 4%. As for frictional coefficients computed by DNS, MR approximate solutions and Landmark software, MR approximate solutions are close to DNS with mean error of 1.8%; however, the results obtained by Landmark software are generally small with the mean error of 23%.