EXPERIMENTAL STUDY OF A GRANULAR MATERIAL FALLING THROUGH A VERTICAL PIPE

Carlos A. Alvarez¹; Erick de Moraes Franklin¹

¹ University of Campinas

doi:10.20906/CPS/COB-2015-0169

Resumo

Generally speaking, modern manufacturing methods of high-technology materials rely heavily on the utilization of granular materials. In many applications, the granular flow depends only on gravity. This paper reports experimental measurements of density waves of granular flows falling down in a vertical tube. In our experiments, the grains consisted of glass beads with diameter within 106 μm ≤ d ≤ 212 μm, flowing down in a 3 mm diameter vertical glass pipe. Under these conditions, density waves appeared and were filmed with a high-speed camera. Density waves are characterized by alternating low and high compactness regions. The wavelength and the celerity of density waves were determined by digital image processing. Experimental results show that the mean wavelength is independent of the mass flow rate, and that the mean celerity has negative values and it has a linear dependence on the mass flow rate.

Palavras-chave: granular flow; density waves; gravitational flow; pipe flow; digital image processing