Viscoelastic properties of magnetic liquids

A. Yu. Zubarev - L. Yu. Iskakova

Department of Mathematical Physics, Ural State University, 620083 Ekaterinburg, Russia

Abstract
Viscoelastic properties of ferrofluids with chain-like internal microstructures are studied theoretically. Our analysis shows that the rheological properties of ferrofluids with internal structures depend strongly both on the magnitude and the direction of an external magnetic field. The viscoelastic properties are especially strong when the field is aligned with the velocity gradient of ferrofluid flow. In this case, the components of complex viscosity as well as the hydrodynamic relaxation time of the system may be several orders of magnitude greater than these characteristics of magnetic liquids with individual particles. We study the influence of magnitude of shear rate on the rheological characteristics of ferrofluids. Destruction of the chains under hydrodynamic forces leads to a fast decrease of effective viscosity and relaxation time with an increasing shear rate. Our results correlate well with known experiments. Figs 4, Refs 9.