An Analysis of Nanoparticle Settling Times in Liquids
  Aggregation and settling are crucial phenomena that involve particulate systems. For particle sizes of millimetre and above, there are reasonable accurate predicting tools. However for smaller particle sizes, there appears to be a void in knowledge. This paper presents an analytical model to predict the settling rates of nano-to-micro size particulate systems. The model was developed as a combination of modified classical equations and graphical methods. A calculation sequence also is presented. By validation with available experimental data for settling nano-to-micro systems, it was found that the two schemes show order of magnitude agreement. A significant feature of this model is its ability to accommodate non-spherical particles and different fractal dimensions. 
D D Liyanage, Rajika J K A Thamali, A A K Kumbalatara, J A Weliwita, S   Witharana
physics.flu-dyn math-ph math.MP