Numerical analysis of non-isothermal viscous jet with peripheral heat transfer

Abstract

A fluid jet ejected from micron size nozzle is a commonly occurring phenomenon in biomedical engineering, printing technology and micro-fluidic applications. Disintegration of a jet into drops occurs due to disturbances induced by external sources. This work explores the various sources of perturbation and their effect on jet disintegration through numerical simulation of a two-dimensional non-isothermal model. The mathematical approach uses a novel technique to combine analytical solutions for the energy balance equation in the radial direction to solve the complete two dimensional problem. The two dimensional energy balance equation is simultaneously solved together with the axi-symmetric Navier–Stokes equations using the slender-jet approximation to predict jet velocity. The energy balance takes into account of peripheral heat transfer to the environment through analytical expressions derived from radial approximations. The model helps in understanding the factors in dynamic temperature variations that eventually render the jet unstable. The distinguishing aspect of this work is the analysis of the effect of a periodic thermal perturbation applied at any point in the domain of a progressive jet, a situation typically encountered in thermal inkjet printers and not considered previously. Results presented for non-isothermal jets which are both stationary and moving illustrate the effect of jet velocity in propagation of perturbation and subsequent drop formation. The major contribution of this numerical study is that it provides an insight on novel ways of controlling droplet formation in bubble jet printers. This study demonstrates that thermal disturbance propagating from periodic heating can be manipulated to shape the droplets and control their breakage point along the jet.