Shear-induced rupturing of a viscous drop in a Bingham liquid

Deformation and breakup of a viscous drop in a Bingham liquid is investigat ed numerically with a volume-of-fluid scheme. Initially, a spherical drop i s placed between two moving parallel plates. For our parameters, the matrix liquid has yielded. The competing effects driving the motion are the shear and interfacial tension. When interfacial tension effects dominate, the dr op evolves to a steady shape which is elongated compared with the case when the outer liquid is Newtonian. Prior to breakup, stress levels are highest at the ends of the elongated drop. When shearing effects dominate, the dro p breaks up, again with features that are elongated compared with the Newto nian counterpart. After the initial breakup, the daughter drops assume stea dy shapes. (C) 2000 Elsevier Science B.V. All rights reserved.