The Investigation of Arch Model Acting in Mass-Flow Hoppers

This paper presents the experimental results of mass-flow hopper arch geometry investigation, which was conducted using a variable geometry plane-flow bin. The cohesive arches formed under different critical outlet openings and hopper half-angles were measured using a 360 degrees two-dimensional laser line scan system. This system was employed to obtain the complete surface profile of each arch across the width of the outlet by moving the rotating laser along the total length of the outlet. The test results were analyzed using Matlab, adopting stationary wavelet transformation 'de-noising' to decrease the signal noise generated during the testing process. The geometric data for each single line scan was smoothed and combined to present a three-dimensional arch surface profile shown to be in good agreement with the observed experimental arch profiles. The angle eta at the intersection of the arch with the hopper walls was then calculated by running a Matlab program and a new angle eta' is introduced to the arch shape study. The detailed results are discussed in the paper. Arch geometry models, such as the parabolic arc and circular arc arch models developed, respectively, by Walker [I] and Enstad [2] are reviewed and their relevance is discussed based on the experimental results presented in this paper.