3D FE—DEM Simulation of a Thickening Growth Model for Japanese Radish Root

The mechanical impedance of soil is well known to influence the shape formation of storage roots of root vegetables strongly. Contact interaction between the root and soil become important in the growth and shape formation of the storage root. This study was aimed at construction of a numerical model for thickening growth of radish tap roots based on the root-soil contact interaction. However in 2D simulation, the height of the soil Discrete Elements increased greatly compared with experimental observations. To solve this problem, 3D simulation was extended and improvements in the shape representation of soil Discrete Elements were made. Soil Discrete Elements with non-spherical shape were generated such that several spherical Discrete Elements were joined together to create a model particle. In this report, the results of preliminary simulation obtained for a small scale are discussed. For the 3D simulation, the shape of root Finite Elements was reproduced based on growth velocities. No distortion occurred in root Finite Elements. Additional examinations of the mechanical properties of radish roots and parameter settings for root Finite Elements are needed. Furthermore, results confirmed that the extension of FE-DEM for the root-soil system in 3D was able to decrease the final height of surface soil Discrete Elements from 18 mm to approximately 14 mm. Clumped Discrete Elements decrease the height to about 13 mm.