Is the angle of repose a measure of the flowability?
The flowability is calculated from the compressive strength of a bulk solid. The compressive strength is dependent on the consolidation stress which has been exerted on the bulk solid before. The more a bulk solid gains strength at a certain consolidation stress, the more difficult it is to initiate flow and, hence, the worse is the flowability. An angle of repose results on properties at the surface of a (often conical) heap, i.e. it is a function of interparticle forces (adhesive forces) and the shape of the particles. Therefore, the angle of repose gives only limited information on the flowability as defined above. The reproducable determination of the angle of repose is not easy (e.g. at fluidizable bulk solid it is of influence, how the material is handled and poured on the heap. In addition, the range of the typical measured angles of repose is relatively small, so that a clear distinction between powders of similar (but different) flow behaviour is not possible.
