CFD simulation of a high-shear mixer for food emulsion production

Mayonnaise is a stable liquid–liquid emulsion with high content of the dispersed oil phase. In the last step of its production, the emulsion is fluxed into a high-shear mixer, where the oil droplets undergo breakage until the final size distribution is reached. This step is crucial to fine-tune the droplet size distribution (DSD), in order to result in the desired structure, stability, taste, and color. In this work, we aim to model this last step via computational fluid dynamics (CFD) and population balance modeling (PBM), to properly describe both the non-Newtonian dynamics of the emulsion and the evolution of the DSD. 2D and 3D CFD simulations show that attention should be paid to the grid resolution to properly describe recognizable patterns observed in experiments. Moreover, CFD and PBM simulations clarify the role of the pre- and post-mixing zones in the high-shear mixer, as well as the effect of the type of flow, pure shear vs elongational, on droplet breakage. We thus propose a physics-based model as a computational tool in order to possibly develop a digital twin of the industrial food emulsion preparation.