- Post Doctoral

## MIT Unit Affiliation:

- Nuclear Science and Engineering

## Lab Affiliation(s):

## Post Doc Sponsor / Advisor:

## Date PhD Completed:

## Top 3 Areas of Expertise:

## Personal Statement:

I am currently working as a Postdoctoral Associate at the Department of Nuclear Science and Engineering (NSE) in the Massachusetts Institute of Technology (MIT).

I worked as a scientific employee at the Helmholtz-Zentrum Dresden-Rossendorf in Dresden, Germany from 2012 to 2015, where I was part of the Department of Computational Fluid Dynamics (CFD) from the Institute of Fluid Dynamics. From 2013 to 2014, I was a visiting graduate (PhD) student and Scientific Support Staff Employee at the Nuclear Science and Engineering Department in MIT.

I obtained my PhD from the Technische Universität Berlin (TU Berlin) in Germany based on my thesis entitled: "Development and Validation of Advance Theoretical Modeling for Churn-Turbulent Flows and Subsequent Transitions". The correspondent research was made off-campus at both the Helmholtz-Zentrum Dresden-Rossendorf and the Massachusetts Institute of Technology.

I got my tittle of Chemical Engineer from the University Simon Bolivar in Caracas, Venezuela. During my time as an undergraduate student I also worked in several extracurricular research programs alongside with the Department of Thermodynamics and Transport Phenomena, and various professors from the University, being able to have my first publications in the areas of oil-water and air-water multiphase flow. After that, I worked at the Institute of Safety Research of the Helmholtz-Zentrum Dresden-Rossendorf as an Intern doing my diploma thesis on "Image analysis techniques for the study of counter-current flow limitation (CCFL) and void fraction during air-water and steam-water two-phase flow in a model of Pressurized Water Reactor (PWR)" in which I used self-developed computational codes which allowed the validation of CFD simulations, as well as the invalidation of various empirical models proposed by other researchers.

Presently, I am working with projects such as the modeling, development, and validation of closure laws for high void fraction regimes in boiling systems, improvements of my image processing software, CFD simulations of oil-water and oil-surfactant-water data and experimental validation of such models through image processing. My current main project for the modeling of slug flow regime is supported by the DOE Sponsored Consortium for Advance Simulation of Light Water Reactors (CASL).

Finally, my career has allowed me to work with people from a large diversity of nationalities, languages, and cultural tendencies during my life in Latin America, Germany, and the USA. I believe that I am a person who can easily and rapidly adapt to new situations and environments.

## Expected End Date of Post Doctoral Position:

## CV:

## Research Projects:

I am working with projects such as the modeling, development, and validation of closure laws for high void fraction regimes in boiling systems, improvements of my image processing software, CFD simulations of oil-water and oil-surfactant-water data and experimental validation of such models through image processing. My current main project for the modeling of slug flow regime is supported by the DOE Sponsored Consortium for Advance Simulation of Light Water Reactors (CASL).

## Thesis Title:

## Thesis Abstract:

The applicability of CFD codes for two-phase flows has always been limited to special cases due to the very complex nature of its interface. Due to its tremendous computational cost, methods based on direct resolution of the interface are not applicable to most problems of practical relevance. Instead, averaging procedures are commonly used for these applications, such as the Eulerian-Eulerian approach, which necessarily means losing detailed information on the interfacial structure. In order to allow widespread application of the two-fluid approach, closure models are required to reintroduce in the simulations the correct interfacial mass, momentum, and heat transfer. It is evident that such closure models will strongly depend on the specific flow pattern. When considering vertical pipe flow with low gas volume flow rates, bubbly flow occurs. With increasing gas volume flow rates larger bubbles are generated by bubble coalescence, which further leads to transition to slug, churn-turbulent, and annular flow. Considering, as an example, a heated tube producing steam by evaporation, as in the case of a vertical steam generator, all these flow patterns including transitions are expected to occur in the system. Despite extensive attempts, robust and accurate simulations approaches for such conditions are still lacking. The purpose of this dissertation is the development, testing, and validation of a multifield model for adiabatic gas-liquid flows at high gas volume fractions, for which a multiple-size bubble approach has been implemented by separating the gas structures into a specified number of groups, each of which represents a prescribed range of sizes. A fully-resolved continuous gas phase is also computed, and represents all the gas structures which are large enough to be resolved within the computational mesh. The concept, known as GENeralized TwO Phase flow or GENTOP, is formulated as an extension to the bubble population balance approach known as the inhomogeneous MUltiple SIze Group (iMUSIG). Within the polydispersed gas, bubble coalescence and breakup allow the transfer between different size structures, while the modeling of mass transfer between the polydispersed and continuous gas allows including transitions between different gas morphologies depending on the flow situations. The calculations were performed using the computational fluid dynamic code from ANSYS, CFX 14.5, with the support of STAR-CCM+ v8.06 and v9.02. A complete three-field and four-field model, including a continuous liquid field and two to three gas fields representing bubbles of different sizes, were first tested for numerical convergence and then validated against experimental data from the TOPFLOW and MT-Loop facilities.

## 5 Recent Papers:

**- "Resolved Interface Taylor Bubble Simulations to Support Eulerian Multiphase Closures Derivation".**

Authors: Gustavo Montoya; Emilio Baglietto.

Computational Fluid Dynamics for Nuclear Reactor Safety Applications – CFD4NRS-6.

Boston, USA. September 2016.

Paper Accepted and presented as Lecture.

**- "A review on mechanisms and models for the churn-turbulent flow regime".**

Authors: Gustavo Montoya; Dirk Lucas; Emilio Baglietto; Yixiang Liao.

Journal of Chemical Engineering and Science (2015).

**- "Implementation and Validation of a Surface Tension Model for the Multi-Scale Approach GENTOP".**

Authors: Gustavo Montoya; Emilio Baglietto; Dirk Lucas.

16th International Topical Meeting on nuclear Reactor Thermalhydraulics - NURETH-16.

Chicago, USA. September 2015.

Paper Accepted and presented as Lecture.

**- "Comparative Analysis of High Void Fraction Regimes using an Averaging Euler-Euler Multi-Fluid Approach and a Generalized Two-Phase Flow (GENTOP) Concept".**

Authors: Gustavo Montoya; Emilio Baglietto; Dirk Lucas; Eckhard Krepper; Thomas Hoehne.

22sd International Conference on Nuclear Engineering (ICONE 22).

Prague, Czech Republic. July 2014.

Paper Accepted and Presented as Lecture and Poster.

“Best Poster Award” received.

**- "Analysis and Applications of a Generalized Multi-Field Two-Fluid Approach for Treatment of Multi-Scale Interfacial Structures in High Void Fraction Regimes".**

Authors: Gustavo Montoya; Dirk Lucas; Eckhard Krepper; Susan Hänsch; Emilio Baglietto.

2014 International Congress on Advances in Nuclear Power Plants (ICAPP 2014).

Charlotte, North Carolina, USA. April 2014.

Paper Accepted and Presented as Lecture and Poster.

“Travel Student Fellowship” received.