Experimental and theoretical investigations on Taylor–Couette flow of ferrofluids subject to magnetic fields

The effect of magnetic fields on flows of ferrofluids enters the basic hydrodynamic equations by an expression for the relaxation of magnetization of the fluid. Despite intense investigations of ferrohydrodynamics, the question of the appropriate approach to describe the magnetization outside equilibrium is still open.By a comparison of experimental and theoretical data of a Taylor–Couette system as a model system, this question is highlighted in this paper. The fluid cell of the Taylor–Couette system is subject to a homogeneous axial magnetic field and the flow profiles are measured by ultrasound-Doppler velocimetry. In this paper, experimental results concerning the transition from circular Couette flow to Taylor vortex flow at different axial magnetic field strengths are measured, compared to theory and discussed.