Modelling of paddy soil using the CFD-DEM coupling method

Abstract

Soil dynamics has been the core of studying the mechanism of soil-tool interaction. However, it is very challenging to study the dynamics of paddy soil that contains a significant amount of water. In this study, a paddy soil model, namely coupling model was developed using the CFD-DEM coupling method. In the coupling model, spherical particles with Johnson-Kendall-Roberts (JKR) surface energy were used to represent paddy soil. The Volume of Fluid (VOF) gas-liquid two-phase flow model was used to represent the characteristics of the water in paddy field. A test and a simulation of soil rotation were performed to calibrate the critical model parameter of soil particle, JKR surface energy. The calibrated value was 2.5 J·m−2, and the relative average error between the simulation and the test was 1.27 %. To verify the accuracy of the coupling model, an experiment of a fertilizer banding opener was conducted in a paddy soil in laboratory conditions. Also, the interaction of the opener with paddy soil was simulated using the coupling model. Then, soil disturbance characteristics and the soil resistance force of the opener were compared between the experiment and model prediction. When using the coupling model to predict, the relative errors were less than 10 % for soil disturbance characteristics and less than 15 % for soil resistance force. This suggests that the model developed using the CFD-DEM coupling method is able to predict the dynamics of soil-tool interaction in paddy fields with reasonably good accuracies.