Regime Map and Triple Point in Selective Withdrawal. Author Zehao Pan, Janine Nunes, Howard Stone Publication Year 2020 Type Journal Article Abstract Entrainment in selective withdrawal occurs when both the top and bottom phases are withdrawn through a capillary tube oriented perpendicular to a flat gravitationally separated liquid-liquid interface. The tube introduces two distinct features to the conditions for fluid entrainment. First, the ratio of the two phases being withdrawn is affected by the region of influence of the flow upstream of the tube's orifice. Second, a minimum withdrawal flow rate must be reached for entrainment regardless of the distance between the interface and the tube. We show that these phenomena can be understood based on the Reynolds number that governs the external flow field around the capillary tube and the capillary number that regulates the effect of the viscosity and capillarity. Journal Phys Rev Lett Volume 125 Issue 26 Pages 264502 Date Published 2020 Dec 31 ISSN Number 1079-7114 DOI 10.1103/PhysRevLett.125.264502 Alternate Journal Phys Rev Lett PMID 33449773 PubMedGoogle ScholarBibTeXEndNote X3 XML