Research Projects

Breakup of bulk liquid into a multitude of droplets, commonly referred to as sprays, is a basic physical processes relevant -- sometimes fundamental -- to a large number of natural processes and applications. Atomizers, as the devices that are employed to achieve this objective are known as, are almost universally dependent on natural instabilities of the liquid-gas interface, formed when bulk liquid is injected in a gaseous environment. Depending on flow conditions and how the geometry of atomizers introduces liquid to the gaseous environment, the resulting spray of droplets can be tailored to specific applications. It is also possible to force instabilities and induce faster breakup or breakup into smaller droplets, but such forcing is rarely employed in existing devices. In this work, we propose to study mechanically-forced, large liquid flow rate injector/atomizers. Specifically, we propose to develop generic designs for such atomizers, perform experiments to evaluate the influence of injector geometry, fluid properties, and forcing parameters on liquid disintegration. The focus will be on large amplitude forcing to excite nonlinear (amplitude-dependent) instabilities, in addition to the commonly employed susceptibility of liquid interfaces to small disturbances that exist naturally in the flow. There are three parts to the investigation, identified to cover the most common atomizer classes: (a) studies on mechanically-perturbed pressure jet, (b) studies on mechanically-perturbed pressure-swirl jet, and (c) mechanically-perturbed pressure jet in a cross flow. In each of the studies, experiments will be design to elucidate the role of injector, forcing, and fluid parameters through regime maps against appropriate non-dimensional parameter; and explain physical mechanisms involved in the process of disintegration of the perturbed jet, specially the effect of high amplitude disturbances. The introduction of high amplitude perturbation requires additional energy. However, it is reasonable to expect that the relation between perturbation amplitude and jet integration is nonlinear in a way that at larger amplitudes the response in disintegration with increasing amplitude flattens -- like most other nonlinear systems. Thus, it is also reasonable to expect that for most cases, optimal forcing may be identified such that further addition of energy leads to increasingly smaller changes in the jet. The project will provide a comprehensive understanding of the effect of frequency and amplitude on jet disintegration for the three classes of injectors.