• computational fluid dynamics (CFD);
  • mixing;
  • finite element method (FEM);
  • mesh superposition;
  • particle tracking


The flow of a viscous Newtonian fluid in a twin sigma blade mixer over the course of a blade cycle is simulated using FEM with mesh superposition, and the resulting velocity profiles are used to calculate the paths of material points in order to do an analysis of the distributive mixing and overall efficiency of the mixer over time. Visual inspection of the material-point distribution, as well as mixing measures that include the cluster distribution index, scale of segregation and mean length of stretch showed the overall mixing effectiveness of this mixer, although there was some positions that had better distributive and stretch capability than others. The mean time-averaged efficiency was related to the specific blade positions and found to remain above zero, while its standard deviation was reducing over time, indicating that the majority of the material points were experiencing equivalent levels of stretching over time. © 2006 American Institute of Chemical Engineers AIChE J, 2006