Investigation of Cross-Sectional Characteristics of Internal Meshing Screw Mixing Flow Field for Dough Paste

The internal meshing screw mixer, driven by extensional rheology, demonstrates excellent mixing efficiency for high-viscosity materials while minimizing fiber damage. This study developed a computational model for the mixing process of high-viscosity fluids based on the motion equations of the internal meshing screw. The model was validated through experiments involving the mixing of corn syrup, flour and water. The results reveal the flow field's cross-sectional streamlines and confirm the presence of chaotic mixing states at the system interface through horseshoe mapping and the existence of hyperbolic points. By comparing the extensional and shear rates, as well as analyzing the distribution of mixing indices, this paper establishes that the primary mixing mechanism within the cross-section is extensional force, highlighting the role of the internal meshing screw as a mixer dominated by extensional flow fields. We investigate the variations in fluid velocity, velocity uniformity index, extensional rate, shear rate, and mixing index over time under different conditions of eccentricity, rotor radius, and rotational speed. The findings indicate that while eccentricity has a limited impact on average velocity, it significantly enhances velocity disturbances and increases the ratio of extensional effects within the fluid domain. In contrast, rotor radius and speed lead to a linear increase in average velocity but have little effect on velocity disturbances and the extensional effects in the fluid domain. This study provides valuable insights into how various cross-sectional parameters influence the flow field of the internal meshing screw mixing process, offering crucial support for its application in mixing high-viscosity non-Newtonian fluids within the food industry.