All You Ever Wanted To Know About Droplets

A team of engineers recently found a new way for determination of droplet size distribution in splattered liquids. The research has proved to be a highly useful one especially with respect to industrial applications like keeping defects at bay in the automotive paint jobs or optimizing farm fertilization. The researches done prior to this in this arena gave an equation that only helped in determination of droplet distribution in simple fluids such as oil or water. These fluids are relatively thinner and more homogenous. But the equation failed to determine the same for non-Newtonian fluids like saliva, paint, or blood.

The researchers were of the opinion that the drawback as result of the stickiness or viscoelaticity of these non-Newtonian fluids. They then conducted an experiment to find out the liquid fragmentation in both kinds of fluids that have three different atomization tests: firstly, these are dropped over a flat surface, next sprayed through a nozzle, and lastly, a spray is formed through collision of two jets. It was observed during the experiments that with the help of a strobe-light technique they could easily create split-millisecond images of these droplets.

The researchers also discovered that, Newtonian liquids, in general, generate a narrower range of droplet sizes as compared to the non-Newtonian fluids. The higher the viscoelasticity of fluids, higher is their capacity to create longer, string-like ligaments before they finally break apart into small and bigger droplets. There were several other features of interest that were discovered by the team here. For instance, more viscoelastic liquids tend to have bumpier ligaments compared to others. However, when a certain extent of viscoelasticity was passed, the ligament bumpiness became constant. Along with, the time needed for ligament to thin out, also became constant for viscoelastic liquids. This time frame is known as relaxation time. Researcher Gareth McKinley adds, “Regardless of the type of experiment, or the kind of polymer or concentration, we see this universal distribution, and it’s broadly applicable to a wide range of fluids.”