Simulation of soil deformation around a tillage tool using computational fluid dynamics

Tillage tool modeling is primarily concerned with analysis of soil deformation patterns and development of force prediction models. During the last four decades, most of the studies conducted on analytical and numerical modeling have considered soil as a solid or elasto-plastic material with quasi-static conditions. Large soil deformation, resulting from the dynamic tool action with respect to the soil mechanical behavior has not been given much attention. This article deals with preliminary modeling of soil deformation around a tool using the computational fluid dynamics (CFD) approach. The main objective of this research was to characterize the soil as a visco-plastic material to determine soil flow pattern around the tool. Analyses were based on the governing equations of non-Newtonian fluid flow with the Bingham constitutive relationship. Simulations were carried out using CFX 4.4, a commercial CFD software. Free-surface simulation of an open channel visco-plastic soil flow indicated soil deformation patterns and the effect of speed on the failure front propagation. Soil deformations, as the flow of a visco-plastic material with yield stress, were observed to possess "plastic flow" and "plug flow" patterns. For a tool speed of 6 m s(-1), with a vertical tool of 20 nun thick and 50 mm wide, operating at 100 nun depth, the soil failure front was observed to be 160 mm at a depth of 10 mm below the top soil surface. The critical speed range was found to be 5 to 65 m s(-1). Further studies with this fluid flow approach are expected to reveal details of dynamic soil behavior with tool interaction.