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Highlights

An image analysis for reconstruction of 3D pore structure within bulk grain was presented.

Abstract. An image analysis technique for reconstruction of the complex 3D pore structure within bulk grain from 2D section images was presented. The technique relies on aligning successive 2D images of cut-sections obtained from colored-wax solidified soybean grain beds, which were then subjected to image processing using ImageJ software developed by the National Institute of Health (NIH, Bethesda, Md.) for the reconstruction and visualization of different airflow paths within the bulk grain. Porosity and tortuosity values were quantified from the 3D image volume and 3D reconstructed inter-connected airflow paths to develop empirical mathematical models for predicting porosity and tortuosity as a function of compaction due to the pressure exerted by the grain depth. Results indicated that the rate of decrease in porosity was higher at the lower compaction grain depth and then gradually approached a minimum value as the compaction grain depth increased. At the top of the compacted grain, the porosity of the tested soybean bed was determined to be 0.42 and reduced to 0.34 at a compaction pressure of 14.2 kPa (equivalent to a compaction grain depth of 25 m). Tortuosity increased with the compaction pressure from 1.15 to 1.58 at a compaction pressure of 14.2 kPa (equivalent to 25 m of grain depth), or by 37.4%.