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Abstract: We investigate the dynamics of microcapsules in linear shear flow within areduced model with two degrees of freedom. In previous work for steady shearflow, the dynamic phases of this model, i.e. swinging, tumbling andintermittent behaviour, have been identified using numerical methods. In thispaper, we integrate the equations of motion in the quasi-spherical limitanalytically for time-constant and time-dependent shear flow using matchedasymptotic expansions. Using this method, we find analytical expressions forthe mean tumbling rate in general time-dependent shear flow. The capsuledynamics is studied in more detail when the inverse shear rate is harmonicallymodulated around a constant mean value for which a dynamic phase diagram isconstructed. By a judicious choice of both modulation frequency and phase,tumbling motion can be induced even if the mean shear rate corresponds to theswinging regime. We derive expressions for the amplitude and width of theresonance peaks as a function of the modulation frequency.



Author: Steffen Kessler, Reimar Finken, Udo Seifert

Source: https://arxiv.org/



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