An analysis of apparent slip flow of polymer solutions

Abstract

Abstract:The apparent slip flow phenomenon of polymer solutions in capillary tubes is analyzed by a thermodynamic diffusion model. An approximate solution of the developing concentration profiles shows a significant decrease in the polymer wall concentration. The approximate concentration profiles are coupled with the concentration-dependent viscosity for aqueous polyacrylamide solutions to provide a priori predictions of the magnitude of the effective slip velocity at the wall. The results are in a reasonable agreement with the available apparent slip data for 1% and 0.5% solutions of partially hydrolyzed polyacrylamide.

In situ rheological characterisation of wastewater sludge: Comparison of stirred bioreactor and pipe flow configurations

“…The correlation for slip proposed by Cohen & Metzner [41,42] for a power law Ostwald fluid can be adapted for a viscoplastic Herschel-Bulkley fluid. This leads to the following equation for the slip volumetric flow rate (Q s ) as a function of the apparent volumetric flow rate (Q): The slip velocity is taken as an empirical power function of the wall shear stress according to Eq.…”

“…The slip phenomenon has been widely described in lots of articles [39][40][41][42][43][44][45] and is known to be due to a drop in solid concentration close to the moving geometry or close to the wall in the case of pipes. The presence of a less concentrated thin layer of lower viscosity close to the wall induces, for a given shear stress a local enhancement of the shear rate.…”

Direct Measurements of Velocity Profiles in Flows of Polymer Solutions through a Rectangular Microchannel with a PDMS Surface

“…7,8) For non-Newtonian fluids many papers also have been already published. [9][10][11][12][13][14][15][16][17][18][19][20] Migler et al 9) directly measured the local velocity of a sheared polymer melt within 100 nm from the solid surface using evanescent light. They reported that polymers slip at all shear stresses in the absence of strong polymer absorption.…”

Slip at Fluid-Solid Interface

“…55,56,75,84,111,120 In some systems, such as microfluidic and viscoplastic, and over certain deformation rate regimes the contribution of wall slip to the total flow rate could be substantial. 23,31,43,55,56,75,84,111,120 In some extreme cases of plug flow, the flow is totally due to wall slip and hence the fractional flow rate becomes unity.…”

“…Slip analysis was pioneered by Mooney 100 who proposed the method of using flow curves from tubes of different sizes to detect and quantify slip. 13,31,54,64,84,101 Wall slip is a very complex phenomenon with no well-developed theory to explain it in its variety 88 and provide accurate predictions with solid experimental foundation. One reason is the difficulty of direct observation and measurement of slip.…”