Advanced DEM simulation on powder mixing for ellipsoidal particles in an industrial mixer

Abstract

Tons of products are facilitated through powder mixing processes. The quality of the final products is highly influenced by the mixing state. Hence, detailed information about the mixing state is necessary to improve the quality. Recent remarkable advancements in computer hardware enable the evaluation of the mixing state via numerical simulation. The Discrete Element Method (DEM) is frequently used in numerical simulations, where computational particle shapes are typically modeled by a spherical body. On the other hand, not all particle shapes in industries are spherical, and the structure of industrial mixers is generally complex. Thus, when the DEM is applied to an industrial mixer, modeling of particle shape and the complex structure of the mixers may be taken into consideration. In the present study, an innovative model is newly developed to simulate the powder mixing of non-spherical particles in an industrial mixer. Here, a non-spherical particle is modeled by the ellipsoidal equation, and an industrial mixer is modeled using the Signed Distance Function (SDF), where the wall boundary shape is flexibly modeled by a scalar field. This approach is referred to as the ellipsoidal DEM/SDF. In the current study, the adequacy and applicability of the ellipsoidal DEM/SDF are demonstrated by the following steps. First, the compatibility of the ellipsoidal DEM with the SDF wall boundary model and the applicability of a soft linear spring in the ellipsoidal DEM/SDF are demonstrated through validation tests. Subsequently, the effect of particle shape on mixing progress in a ribbon mixer is examined. Through computations, the effect of the non-spherical shape is shown to be insignificant on powder mixing progress in the ribbon mixer. Consequently, the ellipsoidal DEM/SDF is shown to be applicable to the industrial powder mixing, and therefore, will contribute to optimization of the mixer design and the operational conditions in chemical, food, and pharmaceutical engineering fields.