Experiment Research Of Magnetic Fluid Flow Characteristics In Microscale

Magnetic fluid is a kind of liquid which is sensitive to magnetic with magnetism and liquidity. Because of its special features, it has been widely applied in the lubrication, sealing, grinding, separation, and biological medicine. To research magnetic fluid flow behavior for the engineering fluid mechanics, biological applications and the understanding of some fluid flow behavior under the force field has important significance.As the development of the liquid microscale flow research work, some scholars has been studying the flow behavior of magnetic fluid under the microscale including the theory research of the magnetic fluid density, viscosity, aggregation, and so on. However, the nonlinear flow characteristics of magnetic fluid under the microscale on experimental study and theoretical research are very few and the regular rules are not yet clear.So in this paper, the flow experiments of magnetic fluid in a circular tube diameter is 50-200 microns by radial magnetic force were carried out to get the root cause of the magnetic fiiud nonlinear flow characteristics in microscale. The research content is as follows:(1) in order to verificate the experiment method and the experimental instrument accuracy to ensure the reliability of the experimental results, the flow experiment device is designed and the experimental error is analysised.(2) Unifromed monodispersed PAA/Fe3O4 magnetic microspheres with ferromagnetism were synthesized acoording to hydrothermal method. Then the unifromed monodispersed PAA/Fe3O4@SiO2 magnetic microspheres with ferromagnetism were synthesized acoording to modified StOber method. And then, different concentrations of PAA/Fe3O4@SiO2 magnetic fluid which has the function of magnetic paramagnetism were prepared with glycerol as base fluid.(3) The flow experiments of magnetic fluid in a circular tube diameter is 50-200 microns by radial magnetic force were carried out which through changing the magnetic field, the concentration of the magnetic fluid, and the size of the circular tube, to study the relationship the average flow velocity in horizontal pipe and the pressure gradient. It got that when the Reynolds number is about 1.4x 10-4, the nonlinear flow characteristic of magnetic fluid under the microscale began.(4) The magnetic fluid flow mechanism in the micro circular tube was studied body force caused by magnetic force, the weakly compressibility of magnetic fluid and viscosity change caused by magnetic force, it got that the root cause of the nonlinear flow characteristic of magnetic fluid under the microscale is viscosity change caused by magnetic force.(5) Fluid motion mathematical model is established with Reynolds number is about 1.4×10-4 for the cirtical value which considering the influence of the viscosity by radial magnetic field force in a micro circular tube and through comparing with the experimental results, the parameters in the model is determined and it got that the model can reflect the characteristics of the magnetic fluid under the micro-scale nonlinear flow.