Investigation of Radial Mixing Dynamics and Saturation Effect in Stirred Brown Rice Granular Systems Using Discrete Element Method

In rice and food processing, spray mixing plays an essential role, with radial distribution uniformity serving as a key metric for assessing mixing performance. However, noticeable variations in the radial migration behavior of brown rice particles can occur even at identical stirring-shaft speeds, and the underlying mechanisms remain insufficiently understood. To clarify the influence of stirring-shaft speed on radial particle mixing, this study employed the discrete element method (DEM) to numerically simulate particle motion under different stirring-shaft speeds. The DEM model was experimentally validated by comparing simulated and measured particle volume proportions and power consumption, thereby ensuring the reliability of the numerical predictions. The results indicate a critical stirring-shaft speed of 20 rpm. Below this threshold, mixing uniformity increases with speed; above it, further increases yield negligible improvement. Analysis of different radial regions shows that selecting an appropriate stirring-shaft speed can effectively improve the mixing homogeneity across layers. In addition, the diffusion behavior of particles in different layers was analyzed, revealing that the diffusion capacity of each layer increases with stirring-shaft speed. These findings offer theoretical support for the optimal design and parameter setting of spray mixing equipment for brown rice and related food products.