Density-difference-driven segregation

• Main Authors: Nai-Wen Hsu, 許乃文
• Other Authors: ‎Shu-San Hsiau
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/19831708083013523860

碩士 === 國立中央大學 === 能源工程研究所 === 102 === The aim of this work is to experimentally investigate how a binary granular mixture made up of spherical glass beads behave when flowing down a straight chute. The mixture was composed by equal sized (3 mm) particles but with two different densities. Four different inclinations combining with two different density ratios are tested. Initially, a binary granular mixture is uniformly mixed. The heavier particles sink to lower levels in the flowing layer while the lighter ones rise toward the top due to the effects of gravity and buoyancy. Finally, the flow becomes completely separated. Processing the sidewall, we are able to measure the evolution of the 2-D concentration and velocity profiles. The volume averaged velocity field of two particles, and granular temperature field are calculated. They help to understand the physical mechanism and dynamic behavior of particles form mixture to segregation. The results show that the intensity of segregation increases with increasing the density ratio of particles, and decrease with increasing the inclinations. The pure-layer, composed of a single constitution, thickens along the direction of flow. Streamwise velocity difference of two particles increases along the direction of flow. And, transverse velocity difference of two particles, before a specific location, decreases along the direction of flow. Granular temperature of lighter particles is slightly larger than heavier ones. Moreover, fixed layer generates if the average Froude number is small. The segregation effect in this state also discussed.