THE BEHAVIOR OF MICROSCALED BROWNIAN PARTICLES IN A CYLINDER UNDER NATURAL-AND MAGNETIC-CONVECTION FLOW FIELD OF AIR

ABSTRACT The behavior of carbon particles (mostly 1μm in diameter) in a natural-convection flow field of air and a magnetic field was studied numerically. One thousand particles were released randomly in a vertical cylinder whose height is equal to its radius. The bottom of the enclosure was heated and the side wall was cooled. A coil with electric current was set coaxially with the cylindrical enclosure. For the nano- and micro- order particles, Brownian motion was taken into consideration and the Langevin equation was solved for the particles. The results show that the behavior of 1-μm-sized particles depends mainly on the flow field. The magnetic field changes the flow mode of natural convection of air due to the paramagnetic susceptibility of oxygen and affects the behavior of the particles indirectly. The coil level, the aspect ratio of the cylinder, and the geometric arrangement of the hot and cold plates produce different flow fields, which makes the behavior of the particles different. The particles larger than 1μm circulate along the streak lines or cluster, but those smaller than 1μm are strongly driven by the Brownian motion.

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