Instability of Jets of Non-Newtonian Fluids

Abstract

The instability and the break-up of liquids is gaining more and more importance in several cases of technical application e.g. for the production of powder out of a melt, for the spray drying and for the atomization of fuel and cooling fluid. Very often an optimal additional treatment and further processing require the production of monodispersed droplets, i.e. the initial disturbance has to be constant and well known. So it happens for instance at the reprocessing of fuel kernels¹ and at the production of liquid-filled capsules². By using additives like long chain polymer molecules to increase the stability of the solutions they receive non-Newtonian characteristics and hinder the occurance of separate droplets because of ligaments in between. A lot of experimental and theoretical work has been done concerning the break-up of Newtonian³ and non-Newtonian^4,5 fluids. In the case of Newtonian systems a linearized stability analysis describes very well the droplet production of a steady lequid jet. The extension to non-Newtonian systems sometimes disagrees with the experimental observations. This paper is restricted to the discription of the ligaments and their formation as it is shown in Fig. 1.