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Magneto-rheological fluid flow in channels with porous walls

This work examines the friction factor of magneto-rheological (MR) fluids in channel flow, where the channel walls are porous surfaces impregnated with MR fluid. There is no flow through the porous walls. Various porosity sizes and different impregnation techniques are utilized in this study. The results are compared to those of a smooth surface. From the experimental results it has been found that under an applied magnetic field, the impregnated porous wall surface would increase the friction factor of MR fluid flow significantly when compared to the smooth surface with the same dimensions. It is also concluded that the impregnation technique affects the amount of iron particles trapped inside the porosities, thus affecting the friction factor. In addition, scanning electron microscopy images of the impregnated samples are taken to qualitatively examine the penetration of MR fluid into porosities. Based on the experimental results a non-dimensional relation for friction factor of MR fluids is developed as a function of Mason number and porosity size. By using this relation, the pressure loss of a MR fluid flowing through a channel with MR impregnated porous walls can be determined without using a constitutive model for MR fluids.