Formation of microdroplets in Newtonian and shear thinning fluids flowing in coaxial capillaries: Numerical modeling

The peculiarities of the Newtonian droplets formation in a Newtonian or non-Newtonian fluid from coaxial capillaries are studied by means of numerical modeling. As a non-Newtonian medium, a shear thinning fluid is considered whose viscosity decreases with the increase of the shear rate according to the Carreau–Yasuda rheological model. It is shown that in the case of a Newtonian continuous fluid, the calculated sizes of the droplets decrease with an increase of the ratio of the flow rates in the outer and inner capillaries which is in a good agreement with experimental data. On the other hand, for the shear thinning continuous medium, droplet sizes become significantly larger than those for the Newtonian fluid. Besides, in the latter case, the droplet sizes weakly depend on the ratio of flow rates of the continuous and dispersed fluids.