CFD modelling of oscillatory perturbed advection in viscous flows

Mechanical oscillation has been proven as an effective method of affecting flow behaviour and material processing of various rheologies. In this work, Computational Fluid Dynamics (CFD) is utilised to investigate the applications of mechanical oscillations in affecting flow and heat transfer in Newtonian and non-Newtonian fluids. Longitudinal oscillations are found to be generally the most effective in producing flow enhancements which exceed those generated by transverse and rotational oscillations. Transverse oscillations, unlike longitudinal or rotational oscillations, generate a vigorous swirling fluid motion and considerable radial mixing in viscous flows, thus, produce large enhancement in wall heat transfer as well as a nearly-uniform radial temperature field. A novel technique which combines transverse oscillation with a step rotation of oscillation orientation is developed and appears to create processing condition that are in great agreement with the high temperature for short time (HTST) assumption, thus, optimising the conventional continuous heat-hold-cool thermal sterilisation processing. CFD results also show that drainage of liquid film of non-Newtonian fluids and settling of spherical particle in non-Newtonian rheologies are affected by superimposed oscillations. The rate of film drainage and settling velocity depends on the vibration intensity and rheological properties