Twin tubular pinch effect in curving confined flows.
Colloidal suspensions of buoyancy neutral particles flowing in circular pipes focus into narrow distributions near the wall due to lateral migration effects associated with fluid inertia. In curving flows, these distributions are altered by Dean currents and the interplay between Reynolds and Dean numbers is used to predict equilibrium positions. Here, we propose a new description of inertial lateral migration in curving flows that expands current understanding of both focusing dynamics and equilibrium distributions. We find that at low Reynolds numbers, the ratio δ between lateral inertial migration and Dean forces scales simply with the particle radius, coil curvature and pipe radius as (Rp(3)R)/a(4). A critical value δc = 0.148 of this parameter is identified along with two related inertial focusing mechanisms. In the regime below δc, coined subcritical, Dean forces generate permanently circulating, twinned annuli, each with intricate equilibrium particle distributions including eyes and trailing arms. At δ > δc (supercritical regime) inertial lateral migration forces are dominant and particles focus to a single stable equilibrium position.
National Research Council of Canada 75 Boulevard de Mortagne, Boucherville (Quebec) J4B 6Y4, Canada.
Liviu
L
Clime
National Research Council of Canada 75 Boulevard de Mortagne, Boucherville (Quebec) J4B 6Y4, Canada.
Keith J
KJ
Morton
National Research Council of Canada 75 Boulevard de Mortagne, Boucherville (Quebec) J4B 6Y4, Canada.
Xuyen D
XD
Hoa
1] National Research Council of Canada 75 Boulevard de Mortagne, Boucherville (Quebec) J4B 6Y4, Canada [2] Institut National de la Recherche Scientifique (INRS) 1650, boulevard Lionel-Boulet, Varennes (Québec) J3X 1S2, Canada.
Teodor
T
Veres