Effect of Confinement on the Aggregation Kinetics of Dilute Magnetorheological Fluids

The goal of this study is to investigate the field-driven structuration of model magnetorheological (MR) fluids in narrow gaps (below 1 mm) for high shear applications. With this in mind, we study the influence of confinement in the aggregation kinetics of dilute carbonyl iron suspensions under strong fields ( λ 10 6 ) in rectangular microchannels using video-microscopy, image analysis and particle level dynamic simulations. Channel widths studied are ranged in the interval [75-1000 m]. In these particular suspensions the experimental and simulation time scales according to: t s ∝ λ − 1 φ 2 D − 2.614 W * − 0.227 , where λ is the Lambda parameter, φ 2 D is the particle surface fraction and W* is the reduced microchannel width. We show that the effect of channel width is crucial in the dynamic exponent and in the saturation (long time) mean cluster size. In contrast, it has no effect in the onset of the tip-to-tip aggregation process.