EPTT 2020

12th Spring School on Transition and Turbulence

Numerical simulation of the primary breakup in a two-fluid thin nozzle

Submission Author: Lucas Ivan de Souza Vereza Medeiros , SC
Co-Authors: Lucas Ivan de Souza Vereza Medeiros, Rafael Velozo, Leonardo Machado da Rosa, Jonathan Utzig, Henry França Meier
Presenter: Lucas Ivan de Souza Vereza Medeiros

doi://10.26678/ABCM.EPTT2020.EPT20-0092

 

Abstract

The atomization of a continuous liquid in a sprayed cloud is a process which is present in several industrial applications, mainly in the petrochemical, agricultural and pharmaceutical fields. The main goal of breaking the liquid into small droplets is to increase their contact area, thus promoting higher evaporation and heat and mass transfer rates. Inside the dispersion nozzle, the liquid filaments can be disintegrated through the kinetic energy itself, by the vibrating and rotating mechanical action of the device or by contact with a gas phase at high relative velocity. The atomization phenomenon is recognized for its high complexity and the wide distribution of drop sizes, caused by the primary and secondary breakup that occurred in the formation of the droplets cloud. Although this is a widely studied phenomenon, the atomization mechanisms are still not completely understood: the data acquisition in regions close to the dispersion nozzle is often limited, which imposes difficulties in understanding the atomization mechanisms, particularly the primary breakup, a phenomenon inherently of random nature. As a consequence, numerical studies associated with atomization are essential for a better understanding of the process. However, the small spatial and temporal scales of the phenomenon make numerical representation difficult due to the high computational effort required. Therefore, this study aims to propose a spatial simplification for simulating a two-fluid nozzle with a pseudo two-dimensional geometry, in order to make spray RANS simulations feasible. With the use of this simplification, it is possible to employ more refined meshes and, consequently, obtain more detailed flow structures. The working fluids considered for the spray simulations were air and water under supersonic conditions. In the numerical simulations conducted, the Volume of Fluid (VOF) method was considered to describe the phases behavior, in which the geometric reconstruction method was used to track the interface. To describe the turbulent flow behavior, the SST k-ω model was used. The equations were solved using the finite volume method, available in a commercial simulator. Due to the nature of the proposed geometry, the comparison with experimental data obtained inside the nozzle becomes an alternative for the validation of the proposed modeling.

Keywords

Sprays, Two-fluid nozzle, primary breakup, Computational fluid dynamics (CFD), Pseudo two-dimensional geometry

 

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