Design and operation of mixing systems using agitated vessels is a difficult task due to the challenge of obtaining accurate information on impeller-induced turbulence. The use of Computational Fluid Dynamics (CFD) can provide detailed understanding of such systems. In this study, experimental tests and computational fluid dynamics simulations were performed to examine the flow characteristics of four impeller designs (anchor, saw-tooth, counter-flow and Rushton turbine), in achieving solution homogeneity. The impellers were used to mix potassium sulfate granules, from which values of electrical conductivity of the solution were measured and used to estimate the distribution pattern of dissolved solid concentrations within the vessel. CFD models were developed for similar mixing arrangement using commercial software, ANSYS Fluent 18.1 solver and the standard k-epsilon (ε) turbulence model. The Multiple Reference Frame (MRF) approach was used to simulate the impeller rotation. Velocity profiles generated from the simulations were in good agreement with the experimental predictions, as well as with results from previous studies. It was concluded that, through CFD analysis, detailed information can be obtained for optimal design of mixing apparatus. These findings are relevant in choosing the best mixing equipment and provides a basis for scaling up mixing operations in larger systems.

Rotary tillage facilitates conservation agriculture in rice-based crop farming systems through minimal soil disturbance for seedbed preparation and crop residue management. However, efficiency of rotary tiller blades is hampered by degraded paddy soils and excessive crop residue conditions. Biomimetics presents an edge in the optimisation design of cultivation tools and can be employed to improve the efficiency of rotary tiller blades. This study was designed to evaluate the adaptability and performance of biomimetic rotary tiller blades inspired by the geometric structure of a mole rat’s claw. Field experiments were conducted to evaluate the blades’ torque and power requirements, soil fragmentation, displacement characteristics, and the rate of straw incorporation at three tillage depths (i.e., 40, 70, and 100 mm). Results revealed that the biomimetic blades minimised torque by up to 21.05%, had lower specific power requirements, and produced finer tilths with granular and more even clod sizes than conventional blades. It also achieved more redistribution of topsoil and improved the straw burial rate. The biomimetic rotary tiller blades are thus energy-efficient and can improve soil structure and the quality of seedbeds, besides managing crop residues through incorporation, and therefore advance conservation tillage in intensive farming systems.