Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 2: SYMPOSIUM: Dynamics of multi-component fluids II

CPP 2.2: Vortrag

Freitag, 4. März 2005, 11:45–12:00, TU C243

Dynamics of elastic micro-capsules in shear flow — •Reimar Finken and Udo Seifert — II. Intstitut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart

The dynamics of elastic capsules with finite bending rigidity subjected to linear shear flow is examined. We present a systematic expansion of the motion of a quasispherical capsule for small deformation and explore the phase diagram of possible motions (tank-treading and tumbling). To first order in the displacements the equations of motion can be reduced to the solution of a tridiagonal system of linear equations. The second order expansion admits a systematic exploration of the tank-treading and tumbling behaviour. The expansion in normal modes is accompanied by numeric simulations of the fluidics.

Shear flow induces regions with compressive and expansive stresses on the membrane. Since elastic membranes cannot resist high compressive stress, they react to compression in one direction by wrinkling, as has been observed experimentally (Walter et al., Colloids and Surfaces A 183-185, 123 (2001)). We present a theory predicting the amplitude and wavelengths of these wrinkles as a function of the elasticity coefficients. This will enable experimentalists to extract elasticitity data from shear flow experiments.