Yield Stress of Magnetic Fluid

Abstract

This paper describes the yield stress of a water-based magnetic fluid having typical concentration and magnetization. Yield stress was estimated from the relationship between shear rate and shear stress in a two-dimensional channel in a low-shear-rate region. When the interaction between magnetic field and flow vorticity is the greatest, yield stress was clearly observed. On the contrary, when the interaction disappeared, yield stress was not observed. Based on these test results, yield stress due to structures of solid particles formed in a magnetic fluid is considered to be very small and the apparent yield stress mentioned above is considered to be due mainly to the interaction between magnetic field and flow vorticity. This idea was verified through a flow resistance test in a circular channel.