Investigating mechanical instability mechanisms in spray flow

This research focuses on the liquid jet in crossflow (LJIC) process, a method used to disperse liquid into a gaseous medium, with applications ranging from fuel injection to advanced plasma spraying. Using computational fluid dynamics (CFD), I investigate how gas viscosity and density influence jet breakup mechanisms, particularly under conditions dominated by Kelvin-Helmholtz (KH) instability. The study employs incompressible Navier-Stokes equations, a geometric volume-of-fluid (VOF) method for interface capturing, and adaptive mesh refinement to achieve detailed simulations. A key focus is on the role of vorticity, as KH vortices significantly impact liquid/gas interface deformation and surface breakup dynamics. Vorticity analysis, performed using the λ² method, reveals that vertical vortices along the liquid column are critical to droplet and ligament formation. The findings show that KH instability governs jet breakup in ultra-high density ratios and low gaseous Reynolds numbers, contrasting with Rayleigh-Taylor instability commonly observed in similar conditions. These insights advance the understanding of vorticity-driven atomization, contributing to the optimization of industrial processes like fuel injection and plasma spraying.

Thermal Spray Process

In the solution precursor thermal spray process, a solution is used as the liquid feedstock suitable for depositing sub-micron-sized particles. This approach simplifies feedstock preparation, reduces costs, and offers greater flexibility in using dopants or mixing multiple components, making it more appealing compared to conventional coating technologies like powder technology. However, accurately screening the solution precursor thermal spray process is challenging because sub-micron particles are formed, and due to this complexity and the lack of knowledge about the intermediate stages of the process, it is currently difficult to predict the behavior of the precursor materials accurately.

The goal is to have a numerical model including a five-stage stages of solvent vaporization, solute precipitation, boiling, thermal decomposition, and melting to predict the final condition of the particle such as particle morphology and shell thickness. Also, the use of submicron-scale particles with a carrier liquid result in improved microstructure and mechanical characteristics, and these powders have been used to synthesize functional metal oxide nanomaterials which can be used for applications in thermal barrier coatings, superhydrophobic coatings, orthopedic implants, and solid-state batteries (SSBs). Lithium cobalt nitrate dissolved in water is used as the solution for producing lithium cobalt oxide, a potential material for the cathode of solid-state batteries.