Numerical Studies of Spray Atomization for Multiphase Flows
Access status:
Open Access
Type
ThesisThesis type
Doctor of PhilosophyAuthor/s
Abbas, FakharAbstract
The current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two ...
See moreThe current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two of them, the volume of fluid (VoF) and the level set (LS), have shown promising findings and have been considered a benchmark for further research. VoF methods have proved good mass conservation behaviour during the advection of solution. However, LS methods have shown better interface representation when used for the calculations of interfacial flows. Most of the recent development in this context either originated from VoF, LS or a combination of both. In the first part of this thesis importance of the current study is highlighted in detail, and an overview of the recent developments for the numerical solutions of immiscible flows is presented. A detailed description of interface-capturing methods and their development over time is presented in a systematic way, leading to the issues addressed in this study. A stochastic field PDF-LES solution of the VoF approach is analyzed against the Sydney needle spray measurements. Solution behaviour for different combinations of stochastic fields and LES grid cells are examined in detail. In the second part of this work, three different LES treatment for unresolved sub-grid fluctuations, TFVoF, TF-AC and newly developed EVD, has been presented. The performance analysis of two already existing solutions, TFVoF and TF-AC, is compared with the EVD approach. Sydney needle spray measurements are used as a benchmark for this comparison. The suitability of the EVD approach is also tested for different flow conditions. Simulation results confirm that sub-grid surface tension plays an important role in the realistic prediction of the jet decay rate, and proper closure models to account for sub-grid surface tension are very necessary. An already existing sub-grid surface tension closure model is incorporated into OpenFOAM and tested for all three LES filtered solutions. The findings of this work suggest that the newly developed EVD approach has shown promising improvements to produce more reliable and realistic solutions for multi-phase flow applications. Sub-volume surface tension closure model, following the EVD formulation, is helpful for more accurate jet decay rate predictions.
See less
See moreThe current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two of them, the volume of fluid (VoF) and the level set (LS), have shown promising findings and have been considered a benchmark for further research. VoF methods have proved good mass conservation behaviour during the advection of solution. However, LS methods have shown better interface representation when used for the calculations of interfacial flows. Most of the recent development in this context either originated from VoF, LS or a combination of both. In the first part of this thesis importance of the current study is highlighted in detail, and an overview of the recent developments for the numerical solutions of immiscible flows is presented. A detailed description of interface-capturing methods and their development over time is presented in a systematic way, leading to the issues addressed in this study. A stochastic field PDF-LES solution of the VoF approach is analyzed against the Sydney needle spray measurements. Solution behaviour for different combinations of stochastic fields and LES grid cells are examined in detail. In the second part of this work, three different LES treatment for unresolved sub-grid fluctuations, TFVoF, TF-AC and newly developed EVD, has been presented. The performance analysis of two already existing solutions, TFVoF and TF-AC, is compared with the EVD approach. Sydney needle spray measurements are used as a benchmark for this comparison. The suitability of the EVD approach is also tested for different flow conditions. Simulation results confirm that sub-grid surface tension plays an important role in the realistic prediction of the jet decay rate, and proper closure models to account for sub-grid surface tension are very necessary. An already existing sub-grid surface tension closure model is incorporated into OpenFOAM and tested for all three LES filtered solutions. The findings of this work suggest that the newly developed EVD approach has shown promising improvements to produce more reliable and realistic solutions for multi-phase flow applications. Sub-volume surface tension closure model, following the EVD formulation, is helpful for more accurate jet decay rate predictions.
See less
Date
2022Rights statement
The author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission.Faculty/School
Faculty of Engineering, School of Aerospace Mechanical and Mechatronic EngineeringAwarding institution
The University of SydneyShare