Regensburg 2007 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 16: Poster Session I

BP 16.13: Poster

Dienstag, 27. März 2007, 17:00–19:30, Poster D

Dynamics of micro-capsules in shear flow using spectral methods — •Steffen Kessler, Reimar Finken, and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57/III, 70550 Stuttgart

Soft objects such as vesicles or micro-capsules in hydrodynamic Stokes flow present a challenging physical model system both from a theoretical and experimental point of view. We present a novel three dimensional numerical approach using spectral methods to simulate the dynamical behaviour of a micro-capsule in a linear shear flow. The shape of the membrane is expanded into a set of smooth basis functions. Using the balance between elastic and hydrodynamic forces and the no-slip boundary condition at the capsule membrane, we derive the equations of motion of the expansion coefficients. This set of coupled nonlinear equations is solved numerically. The mechanical properties of our capsule include resistance to shear, compression and bending. Different constitutive laws and arbitrary external flows can be employed in the code. A viscosity contrast between inner and outer fluid is permitted. We are able to observe relaxation into a stationary tank-treading state, which is also seen in experiments. Numerical results for the deformation and inclination angle agree well with theoretical predictions in the low shear rate limit. The spectral code is used to investigate capsule dynamics beyond the quasispherical approximation.