CDF STUDY OF BIPHASIC FLUID IN CONVERGENT-DIVERGENT DE LAVAL NOZZLE

The biphasic fluid behavior in a convergent-divergent nozzle employed in the Cold spray process is numerically analyzed. Cold spray, also called Cold gas dynamic spray, has a high potential, both for the generation of coatings and for the additive manufacturing technique. Among the projection techniques, the Cold spray technique has some advantages since the particles adhere to the substrate by using high kinetic energy at a relative low temperature. One of the main components of this equipment is the spray gun, its configuration is highly important in the control of the final characteristics of the coating, and in the efficiency of the process. The gun is composed of a de Laval type nozzle, which is a device consisting of a converging and a divergent section with the ability to accelerate compressible fluids at supersonic speeds. The flow itself is driven by a pressure gradient along the nozzle. The behavior of particles into the internal walls of the nozzle, especially in the front part and in the throat itself, is one of the main problems presented by the Cold spray process. This problem causes a decrease in the efficiency of the process due to dimensional variations of the nozzle due to the clogging effect. Previous studies have shown that two of the main factors that cause the formation of agglomerates inside the spray nozzles are the dispersion of the trajectory of the particles and the temperature variations. In this work, a biphasic fluid in a nozzle geometry is numerically analyzed using OpenFOAM under compressible conditions.