Impact of elastic capsules on a solid wall
Department of Mechanical Engineering, Indian Institute of Science, Bangalore, India
Accepted: 9 August 2022
Published online: 29 August 2022
Capsules are ubiquitous in medical and biological systems, and other bio-medical industries. Dynamics of capsules in various flow conditions have received significant attention recently. Various numerical, experimental, and analytical studies have given insight into the dependence of capsule dynamics on the membrane and fluid properties. However, impact of capsules on solid walls has been studied scantily in spite of its relevance in many physical and biological systems. We use numerical simulations to study the impact of a spherical capsule on a rigid surface at moderate Weber (We) and Reynolds (Re) numbers. Specifically, we investigate the effect of shear stiffness and area incompressibility of the membrane on the capsule deformation during impact with a rigid surface using the Neo-Hookean and Skalak constitutive models for the membrane. At low We, the maximum deformation of the capsule scales as We. Whereas, at low Reynolds numbers and high Weber numbers, the maximum diameter to which the capsule can spread after impact, deviates from the We scaling, due to an increase in the viscous dissipation losses during capsule spreading. Interestingly, the scaling at low Re is given by Re which is also in agreement with that for a liquid droplet. We show that, for low area incompressiblity, Neo-Hookean and Skalak models show similar capsule dynamics. Whereas, for capsules with large area incompressibility and low shear stiffness in the Skalak model, the dynamics is similar to that of Neo-Hookean capsules with large shear stiffness.
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