Over the past decades, machines used in grain processing, such as rice whitening mills, have largely been developed empirically. Consequently, the physical mechanisms governing their operation are only partly understood. Traditional vertical rice mills involve complex shear flows of a few grains in confined environments with irregular boundaries [1]. Continuum models struggle to describe such systems due to strong non-local effects and high compressibility. In contrast, direct numerical simulations effectively capture the dynamics of shear flows involving non-spherical particles [2]. In this study, we analyze the mechanics of rice milling by simplifying and reinterpreting its geometry. We transform the original cylindrical setup—comprising a rotating inner cylinder and a stationary outer shell—into a planar model with periodic boundary conditions along the azimuthal direction. The rotating cylinder becomes a flat wall moving linearly, opposed by a stationary wall. A fixed constriction, modeled as a third flat wall perpendicular to the first two, mimics the narrowing found in real mills. Gravity is replaced by a servo-controlled piston pressing vertically on the particles. Rice grains are approximated as spheroids with aspect ratios ranging from one to three. Using the open-source DEM software LIGGGHTS [3], we simulate various applied pressures, shear rates and constriction size. Results show that elongated grains exhibit lower slip velocities near the moving wall due to hindered rotation. These grains tend to align with the flow and orient their smallest cross-section when passing through the constriction. We observe particle pile-up upstream and a low-density region downstream, while pressure locally rises at the narrowing. We analyze the power dissipated in the system and relate it to the degree of milling. This work highlights how simplified, well-controlled simulations can shed light on the intricate physics of rice milling.