Entrance length of oscillatory flows in parallel plate microchannels

Abstract

This paper presents the numerical investigation of the purely oscillatory laminar flows of incompressible Newtonian fluids, in the entrance region of parallel plate microchannels. Development of the axial velocity profiles and the required entrance length were studied in the low Reynolds number regime (20[Formula: see text] 200) and for the low dimensionless oscillation frequency or the Stokes number (1.08 [Formula: see text] 2.80), which is applicable particularly for microchannel flows. To obtain more realistic and applicable results, the time-dependent parabolic entry conditions were considered for all simulations. The results show that for ([Formula: see text]1.53), the entrance length can be estimated by the steady-state results for corresponding inlet velocity profiles, while for the (1.53 [Formula: see text] 2.80), the deviation from the steady-state condition occurs for the entrance length. Further, according to the obtained numerical data, in this work, a useful correlation is proposed to predict the entrance length for the studied ranges of the purely oscillatory flows through the parallel plate microchannels.

Calculation of electro-osmotic flow development length in a rotating three-dimensional microchannel

“…The results demonstrated that the rate of local velocity slip in the wall is always greater than its value in the fully developed region and that as the velocity slip in the wall increases, the pressure gradient in the developing area can be less than that in the fully developed region. Shajari et al (2020) presented a numerical study of fully oscillating Newtonian fluid flows in the entrance region of two parallel-plane microchannels with a time-dependent parabolic inlet velocity. In regimes with low Reynolds and two-dimensional oscillation frequency or Stokes number, the development of the axial velocity profile and the entrance length required for it were investigated.…”