Brownian dynamics simulations on the trapping characteristics of magnetic disk-like particles flowing in a Hagen-Poiseuille flow

Abstract

In the present study, we have elucidated the behavior of a suspension composed of magnetic disk-like particles that flow in a Hagen-Poiseuille flow in a gradient magnetic field and the trapping characteristics of the magnetic particles by means of multi-pairs of magnetic poles. Brownian dynamics simulations were performed in order to clarify the dependence of the trapping characteristics on a variety of factors such as the magnetic interaction between particles, the strength of a non-uniform magnetic field, the strength of the flow field and the separation distance between two pairs of magnetic poles. The main results obtained here are summarized as follows. An increase in the magnetic field strength improves the trapping characteristics of disk-like particles if the influence of an applied magnetic field is sufficiently more dominant than that of a flow field and also that of the magnetic particle-particle interaction. In the case of a strong magnetic particle-particle interaction, thin chain-like clusters are formed from an anchored particle trapped around a magnetic pole. Moreover, if the separation distance between the two poles is sufficiently near, an arch-type cluster is formed between the magnetic poles, and is located in a vicinity area nearer to the wall surface due to the influence of a flow field. For the case of a small aspect ratio r_p=3, in the situation that the particle volumetric fraction is constant, an arch-type cluster formed between the magnetic poles can remain trapped in the vicinity of the wall surface even under the influence of the strong flow field. Hence, we understand that the use of disk-like particles with a small aspect ratio may be able to improve the trapping performance of particles.