Deduction of material characteristics from the relation between slugvelocity and stationary layers

Mode of flow prediction of a bulk material remains a topic of importance within pneumatic conveying. Material characterisation, based on some property of the particle or bulk, involves simple bench-scale testing and has been the standard means of obtaining a convenient classification. Using this method, the boundaries for the various flow types are generally obtained empirically and are not universally reliable. This paper examines an alternative approach, where the unique stationary layer between slugs in horizontal slug flow is examined as a characterisation tool via two theoretically derived constants, which relate to the slug density and the particle exchanges between the slug and stationary layers. The prediction of the constants requires the slug and particle velocities and the layer fraction to be known. As the majority of the existing data in the literature only contains slug velocity and layer fraction values, a method was developed that predicts the constants based only on those inputs. To test the feasibility of the approach, an existing data set that contained a full set of inputs (particle and slug velocities and layer fraction) was used and it was shown the approach can converge to a unique solution and successfully predict the characterising constants. Future work will focus on developing and validating convergence criteria independent of particle velocity data so that the model can be applied to its intended purpose.