Numerical simulation of suppression of forced oscillations of ends of microdroplet aggregates in magnetic fluids at increase of interfacial tension

The relevance of modeling forced oscillations of microdroplet aggregates included in magnetic fluids is associated with the problem of predicting the parameters of working bodies of new devices and to the creation of new magnetosensitive media with controllable properties. The scientific interest is due to the unique sensitivity of microdroplet aggregates to the magnetic field, high magnetic permeability (for liquid media) and low interfacial tension at the aggregate-environmental liquid interface, which makes it possible to obtain forced oscillations of large amplitude. The nature of oscillations depends on the frequency and strength of the external field, as well as on the parameters of the aggregates. The peculiarities of forced oscillations of microdroplet aggregates at large amplitude are poorly understood; in particular, it is of interest to develop a universal modeling method suitable for computational experiments in a wide range of interfacial tension changes and to investigate the possibility of oscillation suppression with increasing frequency, carried out in this work. The modeling of forced oscillations is based on the energy approach and the assumption that the shape of the aggregate elongated along the field can be represented by an ellipsoid of rotation and its magnetization by a linear dependence on the external magnetic field strength. This allowed for a computational experiment with a change in interfacial tension by an order of magnitude in the range from 2 ∙ 10-6 N/m to 2 ∙ 10-5 N/m and obtain satisfactory agreement with the data of full-scale experiments. As a result of computational experiment, it is found that an increase in interfacial tension leads to a decrease in oscillation amplitude and a reduction in elongation, i.e., it suppresses oscillation. Of practical value is the prediction of the deformation of aggregates under the action of a magnetic field for the development of new materials with controllable properties.

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