Theoretical and Experimental Testing of a Scaling Rule for Predicting Segregation in Differently Sized Silos

Abstract

The generalisation of scientific findings between differently sized silos is a challenge faced across many industries. One obstacle is the scaling of material properties (e.g. particle size), process parameters (e.g. the powder feeding rate) and dimensions (e.g. silo diameter and height) to obtain significant results1). The second issue for a meaningful scaling law is maintaining the dynamic similarity between two differently sized silos. A common phenomenon observed when filling alumina storage silos is called air current segregation (ACS,) and was investigated in detail in Zigan et al.2). This paper is now a continuation, exposing the developed scaling rule to a challenging test by replacing alumina with sand particles and the continuum air with water. Results of the scaling tests show that the proposed dimensionless groups do not capture the complete physics. One reason is that using terminal velocity in the scaling law as a physical parameter to lump in fluid and material properties over-simplifies the problem. Another finding is that the particle dynamics in the water model is somehow different from experiments in the air silo.

Keywords

• dimensional analysis
• method of least sum squares
• segregation
• silo
• powder flow
• air current segregation