Abstract Summary (Max 250 words)
In high-viscosity mixing, deformation accompanied by stretching/compression and repeated reorientation plays an important role; however, quantitative methods for evaluating mixing performance have not yet been fully established. This study proposes a performance-evaluation framework for distributive and dispersive mixing based on both numerical analysis and experiments by combining a macroscopic mixing index with a local deformation-mode metric. The target system is a twin-screw mixing device in which the rotation direction and rotational speed of each screw can be independently controlled. The flow patterns are broadly classified into two operating modes: co-rotating conveying and counter-rotating conveying. For flow analysis, the Moving Particle Fully-Implicit (MPFI) method is employed to accurately evaluate the coupled behavior of rotation and deformation. In the simulations, mixing indices based on the redistribution of initially labeled particles are evaluated using either region-based definitions or neighborhood statistics within a prescribed length scale. In addition, local deformation modes, such as shear-dominant and extension-dominant behaviors, and their temporal histories are analyzed using metrics derived from deformation and rotation information. These analyses clarify the mixing characteristics of each operating mode. In the experiments, some Non-Newtonian fluids are used. The time evolution of dye concentration and the number fraction of mixed iron powder are measured. By relating these results to the simulated mixing indices, we discuss mode-dependent differences in mixing performance and their correlation with deformation-related metrics.
