Flow Analysis for Wormlike Micellar Solutions in an Axisymmetric Capillary Channel

Abstract

Flows of wormlike micellar solutions in an axisymmetric capillary channel were studied both numerically and experimentally. In the experimental study, velocity distribution measurements with a particle tracking velocimetry (PTV) were carried out using an aqueous solution of 0.03 mol/1 CTAB and 0.06 mol/1 NaSal as a test fluid. The velocity profile showed a plug-like shape and had infiection points where the velocity gradient rapidly changed. High shear rate regions near the channel walls spread with increasing the average velocity. In the numerical analysis, startup fiows of the CTAB/NaSal solution were computed using a modified Bautista-Manero model as a constitutive equation. Startup flows at a constant average velocity C/or at a constant average pressure gradient -A were numerically simulated. The numerical predictions of velocity profile at steady state agreed with corresponding experimental data. In the constant-[/case, the velocity profile changes from Newton-like to plug-like with time. The infiection points in velocity profile appeared and moved towards the center-side with time. Temporal changes in both velocity gradient and fluidity suggested that the behavior in velocity related the shear-rate-jump property of wormlike micellar solution. In the constant-A case, the region of high shear rate and fiuidity did not spread with time and their profiles temporally changed within this region.

Rheology of wormlike micelles from non-equilibrium molecular dynamics

“…These predictions of the molecular model presented so far are in agreement with recent experiments and predictions worked out by Yamamoto et al [23]. The flow curve for a micellar solution of CTAB/NaSal (cetyltrimethylammonium bromide with sodium salicylate) used by these authors is similar to that shown in Fig.…”

“…Boundary conditions and temperature affect the velocity profiles, gradient-banding and modify the rheological behavior of the system [20][21][22]. In pressure-driven Poiseuille's flow, experiments on flow visualization show regions of turbidity [23], lying almost parallel next to the wall, growing toward the channel center with increasing wall shear rate. These layers can be associated with a secondary flow comprising velocity rolls [24].…”

Pressure-driven flow of wormlike micellar solutions in rectilinear microchannels

“…The two regions are connected by an interfacial transition layer of characteristic width √ ı; which varies as the channel height changes. At the critical pressure drop, a jump in the volumetric flow rate or 'spurt' is predicted which has been observed in experiments [18,19]. To resolve the complex spatial structure of the velocity profile, including the interfacial layer between the two bands and the apparent slip layer at the wall, an adaptive domain decomposition spectral method has been formulated.…”

“…In pressure-driven flows of wormlike micellar solutions the underlying non-monotonic relationship between flow rate and pressure drop along a channel or pipe results in 'spurt phenomena' [17][18][19]. Beyond a critical pressure gradient the classical parabolic velocity profile expected for a Newtonian or Maxwell fluid becomes increasingly plug-like with shear bands forming in the regions of high shear stress near the walls.…”

In situ flow visualization of capillary flow of concentrated alumina suspensions

“…Shear-banded profile was reported in the flow of wormlike micelle solution in slit channel (Fielding and Wilson 2010;Marín-Santibáñez et al 2009;Masselon et al 2008;Yamamoto et al 2008). In the wide channel, this fluid showed change of flow profile from parabolic shape (Poiseuille-like flow) to plug flow with lower viscosity bands closed to the channel wall (Masselon et al 2008).…”