Analysis of the radial flow assumption in a converging model silo

An empirical analysis was carried out on the flow parameters in a converging silo model using the data of Sielamowicz, Błoński, and Kowalewski (2006), obtained using digital particle image velocimetry. The flow was described using the radial flow assumption, and parabolic and Gaussian functions. Using the velocity profiles it was possible to describe vertical velocity values and their dependence on the distance from the outlet. Statistical analysis of the readings taken from velocity profiles was also carried out. The predictions of velocities very close to the outlet of the model hopper were best given by a Gaussian function. Analysis of radial flow indicated that the radial flow assumption did not adequately describe the flow in converging hoppers since the flow did not run radially throughout the whole hopper. Velocity vectors indicated that there was a vertical flow channel. In the upper part of the hopper, there was a combination of both vertical and radial flows and that this form of flow was observed during the whole process of discharge. A modification of the radial flow model was shown to adequately describe velocities only at some distance away from the outlet.