Study on the flow characteristics of air-to-solid ratios for pneumatic conveying of wheat based on computational fluid dynamics: discrete element method

Abstract

To optimize the efficiency and stability of wheat pneumatic conveying systems, this study systematically analyzed the flow characteristics under varying air-to-solid ratios using the CFD-DEM (Computational Fluid Dynamics—Discrete Element Method) approach. The results demonstrate that as the gas velocity increases, the flow regime within the pipe transitions progressively from plug flow to dune flow, and ultimately to stratified flow. The standard deviation of inlet pressure fluctuations was highest under dune flow conditions, followed by plug flow, and lowest during stratified flow, while the system stability showed the inverse trend. Wheat particle velocity is highest under stratified flow conditions, followed by dune flow, and lowest during plug flow. The distribution of wheat particles transitions from a fully filled pipe state to a depositional state at the pipe bottom. Increasing the wheat feed rate reduced both the particle velocity growth rate and system stability. This study demonstrates the critical role of the air-to-solid ratio in regulating flow regimes to influence conveying stability and efficiency, providing direct guidance for optimizing air-to-solid ratio settings in wheat processing lines.