Graphical Presentation of Transformation of Tomography Data for Gravitation Silo Flow

Z. Chaniecki1, M. Niedostatkiewicz2, D. Sankowski1

1Technical University of Lodz, Computer Engineering Department, Lodz, Poland, Email: zch@kis.p.lodz.pl, dsan@kis.p.lodz.pl

2Gdansk University of Technology, Department of Fundamentals of Building and Material Engineering, Gdansk, Poland, Email: mniedost@pg.gda.pl

ABSTRACT

The graphical presentation of the data from Electrical Capacitance Tomography (ECT) is presented. The measurements were obtained during the gravitational discharge process of a laboratory silo for non-cohesive (dry sand) and cohesive solids (mixture of sand and glycerine). The experiments were performed both for different initial densities (loose and dense bulk solids) and with different wall roughness (smooth and very rough walls). Changes of the dielectric permittivity proportional to changes of the bulk solid porosity were measured at height h = 0.5 m and h = 1.5 m from the bottom of the silo during the whole gravitational silo emptying process. The results are presented for raw and reconstructed data. The changes of porosity during experiments were discussed on the basis of the distribution of the average concentration of the solid at the concentration areas. Porosity distributions were presented in the 2D representation (tomograms – typical cross sections, also topograms – longitudinal view of the dynamic process) and continuous characteristics. Graphical presentations of alternations of the concentration of the bulk solids, especially for cohesive solids, were compared with the results of measurement of the vertical acceleration registered on the silo wall at height h = 1.0 m giving extra information about process dynamics. Graphical presentation of changes of the material concentration, estimated during the discharging process, give significant information about the process. It allows for the continuous observation of a process, contrary to the analysis of single tomograms in certain instant slices.

Keywords: Electrical Capacitance Tomography, flow imaging, granular materials, silo, gravitation discharge, graphical presentation of flow, raw data, reconstructed data