Effect of moisture content on flowability: Angle of repose, tilting angle, and Hausner ratio

The angle of repose, angle of tilting, and Hausner ratio are frequently used to estimate the flowability of a particulate material. In this study, these factors were determined for 12 samples as a function of the moisture content. The measurements were thoroughly analyzed and indicate that the angle of tilting is the most appropriate for describing a material's response to moisture content. The flowability results clearly showed three types of materials according to their response to moisture content: solid particles, porous particles, and size-changing particles. A thorough analysis of various sizes of spherical solid particles enabled the identification of five zones from dry to fully immersed in water, and a zone map could be obtained. In addition, a model predicting flowability as a function of moisture content and Archimedes number could then be developed. Further experiments are required to relate the zone map and model to other types of materials.