BREAKUP OF NEWTONIAN AND NON-NEWTONIAN FLUIDS IN AIR-JETS

The breakup of droplets of non-Newtonian fluids has been investigated by high speed photography and impaction following preliminary results of Newtonian fluids, which confirmed the suitability of the measuremen t techniques. Single droplets with diameters from 2.4 to 3.3 mm, were arranged to fall under gravity into a jet of air with velocities up to 360 m/s. The droplets of Newtonian fluids, water and Diesel oil, were atomised in the expected manner within three main regimes characteris ed by the Weber number of the droplet and air jet conditions, while si milar droplets of non-Newtonian fluids were found not to atomise but t o develop under shear and stretching into ligaments of fluid separated from a local region of their surface; these ligaments were elongated until breakup occurred, though not into small droplets as with the New tonian fluids. Some of the non-Newtonian fluids (TEP with 7.5% and 10% K125, with and without water) were found not to break up at the maxim um speed of the tests and they will be re-examined at higher jet veloc ities. Increase in the concentration of K125 in TEP resulted in higher critical speed for a given droplet diameter.