Naylor M A, Swift Michael R, King P J
School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, England.
Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Jul;68(1 Pt 1):012301. doi: 10.1103/PhysRevE.68.012301. Epub 2003 Jul 21.
A large heavy object may rise to the top of a bed of smaller particles under the influence of vertical vibration, the "Brazil nut effect." Recently it has been noted that interstitial air can influence the Brazil nut rise time. Here we report that the air movement induced by vertical vibration produces a very strong Brazil nut effect for fine granular beds. We use a porous-bottomed box to investigate the mechanism responsible for this effect and to demonstrate that it is related to the piling of fine beds, first reported by Chladni and studied by Faraday. Both effects are due to the strong interaction of the fine particles with the air, as it is forced through the bed by the vibration.
在垂直振动的影响下，一个大的重物可能会上升到较小颗粒床层的顶部，即“巴西坚果效应”。最近人们注意到，间隙空气会影响巴西坚果的上升时间。在此我们报告，垂直振动引起的空气流动对细颗粒床层产生了非常强烈的巴西坚果效应。我们使用一个底部多孔的盒子来研究造成这种效应的机制，并证明它与细颗粒床层的堆积有关，这一现象最早由克拉尼报道，并由法拉第进行了研究。这两种效应都是由于细颗粒与空气的强烈相互作用所致，因为空气在振动作用下被迫穿过床层。
