Measurement of shear rate on the surface of a cylinder submerged in laminar flow of power-law fluids

• Published in: Experimental thermal and fluid science 2012-05, Vol.39, p.167-175
• Main Authors: Sabiri, N.-E., Chhabra, R.P., Comiti, J., Montillet, A.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Cylinder; Cylinders; Electro-diffusional flow diagnostics; Exact sciences and technology; Fluid dynamics; Fluid flow; Fluids; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Laminar flow; Micro-electrodes; Newtonian fluids; Non-newtonian fluid flows; Physics; Shear rate; Shear-thinning fluids; Viscosity
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2012.01.021

► The electrochemical polarographic technique is used to measure the local shear rate. ► The local shear rate on the cylinder surface with Newtonian and non-Newtonian fluids. ► The influence of shear-thinning viscosity on the distribution of shear rate. ► The maximum shear rate shows a positive dependence on the Reynolds number. ► The results are borne out by both experiments and idealised 2-D simulations. Micro-electrodes made of platinum have been used to measure the local shear rate on the surface of a cylinder (length-to-diameter ratio of 11–12) exposed to the fully developed laminar flow of power-law fluids in a vertical pipe. Two Newtonian and two shear-thinning solutions are used as model test fluids to ascertain the influence of shear-thinning viscosity on the distribution of shear rate on the surface of the cylinder. The results reported herein encompass a wide range of Reynolds numbers 0.16⩽Re⩽75 based on the cylinder diameter and centreline velocity. Over the range of conditions, it is observed that the shear rate is a maximum at about θ=130° and it tends to be higher in shear-thinning fluids than that in Newtonian fluids otherwise under identical conditions.