A Numerical Simulation of Enhanced Mixing of a Non-Newtonian Fluid in a Cavity with Asymmetric Non-Twin Rotors

Novel non-twin rotors are developed to introduce a symmetry break to enhance the mixing in a cavity. The novel rotors co-rotate and have different geometries with a speed ratio of 2. Numerical simulations are carried out using a finite element scheme with the mesh superposition technique. The time-dependent flow field of a non-Newtonian fluid obeying the Bird–Carreau constitutive model is solved. Mixing details are analyzed with regard to particle tracking, tracer evolution, an invariance index, and the Manas-Zloczower mixing index. The numerical results reveal that the bifurcation (cutting) action occur in the clearance between the rotors when the strips of material closely approach the upper and lower intermeshing zones. A similar Baker’s transformation is found to control the whole mixing process, especially in the non-twin group where asymmetric rotors provide more opportunity to achieve the cutting and reorientation of fluid striations. The results confirm that the new geometry provide better distributive and dispersive mixing than the commonly used traditional twin rotors.