화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.51, No.51, 16755-16762, 2012
Wall Retardation Effects on Flow and Drag Phenomena of Confined Spherical Particles in Shear-Thickening Fluids
In this work, effects of the wall retardation, Reynolds number, and shear-thickening viscosity behavior of fluids on flow and drag phenomena of confined spherical particles are presented. The governing mass and momentum conservation equations are solved using computational fluid dynamics-based commercial software. The numerical solver is thoroughly validated by comparing present results with existing literature for the case of unconfined spheres in Newtonian and shear-thickening fluids. Extensive new results were presented in the following range of conditions: Reynolds number, Re, 1-100; wall factor, lambda, 2-5; and power-law index, n, 1-1.8. The wall factor (lambda) is defined as the ratio between the tube diameter and the particle diameter. The severity of wall retardation effects increases with increasing power-law index. For fixed values of the Reynolds number, the recirculation wake length decreases with decreasing wall factor and/or increasing power-law index. For n = 1.8, the wall retardation effects are very strong so that for lambda = 2, there is no recirculation wake behind confined sphere even at Re = 100. Furthermore, regardless of values of the Reynolds number, the total drag coefficient increases with increasing power-law index and/or decreasing wall factor. The effect of the Reynolds number on the ratio between pressure and friction drag coefficients decreases with increasing power-law index and/or increasing wall factor. Finally, on the basis of present numerical results, a correlation is developed for the total drag coefficient of confined spherical particles settling in shear-thickening fluids.