Abstract
The influence of particle size on segregation phenomena in two-dimensional binary granular mixtures with a similar solid fraction under vertical vibrations is experimentally investigated in this study. Four different particle size ratios (Dl /Ds ) are varied. The granular mixtures are subjected to vertical vibrations under six different dimensionless accelerations (Γ = 1-6), with constant vibrational amplitude of 5 mm. The vertical segregation coefficient (H ) is here introduced to analyse the degree of segregation of the mixtures. We found that the Brazil nut effect, where the larger particle rises to the top, is observed for all the tests whenever the segregation is occurred. The degree of segregation of the mixtures is a function of the coefficient H , which can be divided into 3 zones: a compaction zone with particle mixing (0.0 ≤ 0.2), a partially segregated zone (0.2 ≤ 0.4), and an apparently segregated zone (0.4 ≤ 1.0). The segregation begins when Γ ≥ 2 and then tends to increase when Γ is increased. In addition, the segregation is quite clearly found when Dl /Ds ≥ 3 and Γ ≥3.
Highlights
Since granular media are composed of grains with various physical properties such as size, density, friction and rigidity, complex behaviours of granular media are generally observed
The influence of the particle size ratio (Dl/Ds) and the dimensionless acceleration (ī) on segregation of the binary granular mixture is described by means of such vertical segregation coefficient
The objective of this study is to experimentally investigate the effects of the particle size ratio (Dl/Ds) and the dimensionless acceleration (ī) on granular segregation in the binary mixture subjected to vertical vibrations
Summary
Since granular media are composed of grains with various physical properties such as size, density, friction and rigidity, complex behaviours of granular media are generally observed These behaviours are cannot be classified into common substances [1, 2]. “Segregation” is one of the interesting phenomena observed when a homogeneous bulk solid constituted from a variety of species or components evolves from an initially mixed state to a presumed non-uniform state owing to the relative movement within the materials [3, 4] This is an unwanted phenomenon often occurring in many industrial areas associated with the handling and processing of granular mixtures such as pharmaceuticals, food processing, geophysics, material sciences, and almost all engineering fields. We have accepted for a long time that the segregation phenomena in granular media occurs from a difference of their physical properties (e.g. size, density, shape, etc.), a significant factor to control segregation in many industrial processes is the particle size [3, 5,6,7]
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