Simulation and Validation of Airflow Pressure Patterns in Hopper-Bottom Bins Filled with Wheat

Abstract. A non-linear model that can explain the three-dimensional airflow pressure patterns in grains was developed and solved using the finite element method. The model can simulate airflow distribution in both flat-bottom and hopper-bottom bins of different shapes such as square, rectangular, or cylindrical. Resistance to airflow through the grain bed was explained using a modified form of Darcy’s equation. The airflow model was validated against experimental data obtained from studies conducted in a 4.72 m diameter hopper-bottom bin filled with wheat, aerated using a 1.82 m vertical rocket-type aerator. The relative error between the experimental and predicted static pressure values for the entire bin geometry was less than 3.2%, with higher values at regions near the aerator. The validated model can be used to predict the static pressure patterns and airflow distribution (because airflow lines are perpendicular to iso-pressure lines) in various grain beds and can handle variations in product type, moisture content, grain surface configurations, foreign material content, direction of airflow, and aeration duct designs. Using the validated model, airflow pressure patterns in a hopper-bottom cylindrical bin with 10 different duct configurations were predicted and results were discussed for their implications for aeration and near-ambient air drying. The airflow pressure patterns as affected by variations in airflow rate, grain surface configuration (peaked, levelled and conically cored), bin geometry, direction of airflow, and grain bed height (grain filled up to 40%, 60%, and 80% of the bin height) were also simulated and discussed.