1. The unsteady drag of a translating spherical drop with a viscoelastic membrane at small Reynolds number
- Author
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Vivek Narsimhan and Nader Laal Dehghani
- Subjects
Physics ,010304 chemical physics ,Applied Mathematics ,Mechanical Engineering ,General Chemical Engineering ,Drop (liquid) ,Reynolds number ,Mechanics ,Stokes flow ,Condensed Matter Physics ,01 natural sciences ,Viscoelasticity ,Quantitative Biology::Cell Behavior ,010305 fluids & plasmas ,Quantitative Biology::Subcellular Processes ,Physics::Fluid Dynamics ,symbols.namesake ,Viscosity ,Membrane ,Drag ,Stokes' law ,0103 physical sciences ,symbols ,General Materials Science - Abstract
This manuscript quantifies the hydrodynamic drag of a spherical droplet translating in unsteady Stokes flow when the droplet has a thin, complex membrane. All forces (e.g., Stokes drag, Basset forces, unsteady memory forces, etc.) have the same functional form as the drag of a clean spherical droplet, as long as one replaces the interior viscosity with an effective (frequency-dependent) one that depends on the viscoelastic moduli of the membrane. The shear elastic moduli of the membrane do not modify the unsteady drag of the droplet – only the dilatational modes matter. We demonstrate how this result can be obtained using simple symmetry/scaling arguments. The results are written for any linearly viscoelastic membrane, but we in particular examine the cases of a purely viscous membrane, purely elastic membrane, one-mode Maxwell membrane, and one-mode Kelvin-Voigt membrane. For the latter two models, we quantify how the membrane relaxation time alters the time-dependent motion of the droplet.
- Published
- 2019
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