高密度魔晶球在剪力影響下之流動
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2015
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Abstract
我們使用影像分析有彈性的光滑軟顆粒材料（魔晶球）在三維空間中的運動。在雙錐形邊界條件之下，上板以穩定角速度轉動，下板則靜止不動，使魔晶球被一穩定的剪力驅動。在此系統條件底下魔晶球表現出過滲透的行為，並且均方位移曲線（MSD）表現出類週期性的震盪行為，其第一周期曲線增長與魔晶球在水缸內的高度有關。隨著魔晶球所在位置垂直高度的增加，MSD曲線增長至第一高峰值的速率也越快，並且魔晶球的運動行為由角度方向(φ)分量主導。在受穩定剪力影響下的魔晶球運動與同狀況下的牛頓流體之運動行為差異很大，但也不是無序且隨機的布朗運動行為。
We study the three-dimensional motion of a kind of elastic and soft particles with smooth surface, hydrogel spheres, by video imaging. The spheres are subjected to steady shear with the setup of double-cone geometry. In our system, the upper cone is driven by a motor and has constant angular velocity while the lower cone is fixed. The spheres exhibit super diffusion behavior, and the mean square displacement (MSD) shows quasi-periodic behavior with height-dependent periods. The MSD curve increases faster when the height increases before it climbs up to the first peak. The motion of the hydrogel spheres is dominated by the motion in φ direction. In our system the motion of the hydrogel spheres is much different from that of the Newtonian fluid under steady shear and also different from the Brownian motion.
We study the three-dimensional motion of a kind of elastic and soft particles with smooth surface, hydrogel spheres, by video imaging. The spheres are subjected to steady shear with the setup of double-cone geometry. In our system, the upper cone is driven by a motor and has constant angular velocity while the lower cone is fixed. The spheres exhibit super diffusion behavior, and the mean square displacement (MSD) shows quasi-periodic behavior with height-dependent periods. The MSD curve increases faster when the height increases before it climbs up to the first peak. The motion of the hydrogel spheres is dominated by the motion in φ direction. In our system the motion of the hydrogel spheres is much different from that of the Newtonian fluid under steady shear and also different from the Brownian motion.
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Keywords
顆粒流, 顆粒體, Granular flow, Granular material