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Minuet motion of a pair of capsules interacting in simple shear flow

Abstract : We study the three-dimensional hydrodynamic interaction of a pair of identical, initially spherical capsules freely suspended in a simple shear flow under Stokes flow conditions. The capsules are filled with a Newtonian liquid (same density and viscosity as the suspending fluid). Their membranes satisfy the neo-Hookean constitutive law. We consider the rarely studied case where the capsule centres are initially located in (or near) the plane defined by the flow direction and the vorticity vector, i.e. in two different shear planes. The motion and deformation of the capsules are modelled by means of a boundary integral technique to compute the flows, coupled to a finite element method to calculate the force exerted by the membranes on the fluids. We follow the motion and deformation of the capsules as they are convected towards each other after a sudden start of the flow. Our main finding is that, depending on their initial position and deformability, the two capsules may oscillate slowly about the flow gradient axis, get nearer to each other at each oscillation to finally interact strongly and separate. This minuet motion had not been identified previously. We identify the regions of space where either simple crossing or minuet occur. This phenomenon has a marked influence on the irreversible trajectory drift of two capsules after crossing: the minuet process leads to a significant trajectory displacement along the flow gradient when none was expected, based on the previous studies where the two capsules had a significant relative velocity.
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Contributor : Anne-Virginie Salsac <>
Submitted on : Saturday, June 6, 2020 - 3:32:32 PM
Last modification on : Monday, July 27, 2020 - 1:00:05 PM


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X.-Q. Hu, X.-C. Lei, Anne-Virginie Salsac, Dominique Barthès-Biesel. Minuet motion of a pair of capsules interacting in simple shear flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2020, 892, pp.A19. ⟨10.1017/jfm.2020.181⟩. ⟨hal-02818230⟩



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