Wall Retardation Effects on Flow and Drag Phenomena of Confined Spherical Particles in Shear-Thickening Fluids
2012
Rajasekhar Reddy, C. | Kishore, Nanda
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, λ, 2–5; and power-law index, n, 1–1.8. The wall factor (λ) 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 λ = 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.
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