EPTT 2020

12th Spring School on Transition and Turbulence

ANALYSIS OF THE EFFECTS OF TURBULENCE CLOSURE MODELS ON WALL FILM MODELLING

Submission Author: Bruno Silva de Lima , MG
Co-Authors: Francisco Souza, Bruno Silva de Lima, João Rodrigo Andrade, Carlos Duarte
Presenter: Francisco Souza

doi://10.26678/ABCM.EPTT2020.EPT20-0041

 

Abstract

Liquid film formation is a phenomenon widely found in industrial processes. Intended or not, it can be found in process such as coating, painting, steam power generation, refrigeration systems, fuel injection among others. For instance, the injection of fuel in an internal combustion engine is subjected to wall impingement, which directly affects the outcome of the combustion process. Many methods for measuring and predicting these phenomena have being developed including physical experiments as well as numerical-computational techniques. The improvement in the characteristics of this process makes it more efficient and less environmentally degrading. In order to improve these process a fundamental step is the understanding of the physics involved. For such purpose, numerical simulations have been increasingly used in complex engineering problems, providing results in scenarios where experiments may not be feasible. The Computational Fluid Dynamics (CFD) approach has proven a powerful, valuable tool to reach the state-of-art in engineering, reducing costs and development time. To test the stability of the models in predicting liquid film formation, different turbulence closure models were used to test the Eulerian Wall Film (EWF) model in the current work. The EWF model was designed to model the splashing of Lagrangian droplets on a wall surface and the consequently thin liquid film generation. The model is derived from classical fluids mechanics theory and accounts for mass and momentum conservation. This model uses a two dimensional form of mass and momentum conservation for the liquid phase in a three dimensional mesh. To verify the employed models, the numerical results are compared with a cross flow physical experimentation developed by Shedd et al (2009). The current implementation was carried out using an in-house code. The code is called Unscyfl3D and it is being developed by researchers at Federal University of Uberlândia, and validated for a wide range of cases. The software is based on the analysis of incompressible flows using finite volume method in unstructured meshes. To coupe velocity and pressure the SIMPLE algorithm is used. To store the variable a collocalized arrangement is used. The numerical scheme for diffusive terms is the second order centered differences and for the advective terms the second order upwind. The secondary break up model for the Lagrangian droplets is the ABTAB. The main results showed that the breakup model proved to be sensitive against the turbulence closure model. This fact directly affects the liquid film formation while the droplets distribution inside the domain affects the splashing probability, which is a fundamental step on the EWF model.

Keywords

Thin liquid film formation, Liquid jet in cross flow, Eulerian Wall Film (EWF)

 

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