Entry Flows of Polymer Solutions through a Planar Contraction in a Microchannel

Abstract

Flows of polymer solutions through a 3.7:1 abrupt contraction were observed in a micro-and a regular-size channels with rectangular cross sections. The test fluids are three kinds of 0.2 wt% aqueous solutions of polyacrylamide whose rheological properties are different with each other. In the previous works, apparent slips were observed on the channel wall for the polymer solutions and the slip levels of these solutions are considered to be different. In the present paper, the growth of the salient corner vortex is discussed as a function of the shear rate. Consequently, the vortex size in the microchannel is larger than that in the regular-size channel for the flow of polymer solution whose slip level is weak, whereas the vortex size in the microchannel is smaller than that in the regular-size channel for the flow of polymer solution whose slip level is strong.

Slip flows of Newtonian and viscoelastic fluids in a 4:1 contraction

“…The few exceptions that we are aware of regarding contraction flows with wall slip, are the numerical works of Sunarso et al [23,24] investigating the effect of wall slip on the flow behavior in macro and micro contraction channels, Yasuda and Sugiura's [25] experimental and numerical studies of contraction flows with the nonlinear Navier slip boundary condition, and the analytical study of inertialess planar contraction flow of Joshi and Denn [26] with the linear Navier slip boundary condition. Although Sunarso et al [23,24] have analyzed this problem, they used a different constitutive equation (single mode FENE-P model) and their investigation is limited to a small range of slip coefficients.…”

Flow visualization and velocity measurement in a small-scale open channel using an electron microscope

“…A number of studies on velocity distribution measurement of micro-scale flows have been conducted using optical microscopes [12,13]. In micro-scale flows, numerical simulation based on a continuum model, such as the Navier-Stokes equation, was carried out while taking into account the flow characteristics for micro-scale phenomena, such as wall slip [14].…”