Rafael Gontijo

Rafael Gontijo
University of Brasília | UnB · Engenharia Mecânica

PhD - Fluid Mechanics

About

51
Publications
11,551
Reads
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190
Citations
Introduction
Prof. Rafael Gabler Gontijo lectures Fluid Mechanics and related topics at the University of Brasília- Brazil. He is a Mechanical Engineer with a Masters Degree and a PhD in Mechanical Sciences. He was also a Professor of the Energy Department of the State University of Campinas (Unicamp-Brazil) for 2 years, where he is now a Visitant Professor supervising graduate students and coordinating a research lab on hydrodynamics of Magnetic Fluids. https://www.youtube.com/user/rafaelgabler/featured?v
Additional affiliations
November 2013 - present
University of Brasília
Position
  • Professor (Associate)
November 2013 - present
University of Brasília
Position
  • Professor (Associate)
Description
  • Fluid Mechanics II (Intermediate Fluid Mechanics), Hydrodynamics of Magnetic Fluids, Experimental Fluid Mechanics
April 2009 - October 2013
University of Brasília
Position
  • Professor (Assistant)

Publications

Publications (51)
Article
Full-text available
In this work, computational fluid dynamics simulations of a ferrofluid plane Poiseuille flow in the presence of a constant applied magnetic field are performed. The orientation of the field is perpendicular to the direction of the flow. An original numerical methodology for calculating magnetic and hydrodynamic fields is proposed, including an impo...
Article
Full-text available
This work investigates the effects of an applied magnetic field on the laminar flow of a ferrofluid over a backward-facing step. Both constitutive equation and global magnetization equation for a ferrofluid are considered. The resulting formulation consists in a coupled magnetic-hydrodynamic problem. Computational simulations are carried out in ord...
Article
Full-text available
This work aims to reconstruct a continuous magnetization profile of a ferrofluid channel flow by using a discrete Langevin dynamics approach for the fluid’s micro structure. The continuous magnetization field is obtained through the coupled solution of 2D Ferrohydrodynamics equations in a CFD approach using a numerical code developed by the authors...
Article
Full-text available
In this work, we perform Langevin dynamics simulations to examine microstructure-macroscopic related properties of magnetic fluids in an attempt to understand the influence of the long range viscous hydrodynamic and dipolar interparticle interactions on the complex susceptibility response of a magnetic suspension undergoing an oscillatory magnetic...
Article
Full-text available
This work presents a theoretical, numerical and experimental investigation on the shape and vertical displacement of a free surface formed in the interface between a magnetic fluid and a non-magnetic one. The magnetic fluid is confined between two parallel vertical flat plates. The presence of an external magnetic field applied by a permanent magne...
Article
This work presents important additional discussions regarding our recent publication: Heat transfer increase for a laminar pipe flow of a magnetic fluid subjected to constant heat flux: an initial theoretical approach. In our first paper we proposed a theoretical law to predict the mean Nusselt number for a laminar pipe flow of a magnetic fluid sub...
Article
This work presents a theoretical law to predict the mean Nusselt number for a laminar pipe flow of a magnetic fluid subjected to an uniform magnetic field. The intensity of the field, the magnetic susceptibility of the fluid and the orientation angle formed between the magnet and the direction of the flow appear explicitly in the final expression o...
Presentation
Full-text available
Short presentation on the 70th Annual Meeting of the APS Division of Fluid Dynamics discussing the interplay between long range hydrodynamic and magnetic particle interactions in suspensions of solid magnetic particles immersed in a Newtonian carrier liquid. In this short talk I discussed how the dispersive nature of hydrodynamic interactions could...
Technical Report
Full-text available
This work consists of performing a theoretical, numerical and experimental study to determine both the shape and vertical displacement of a free surface formed on the interface between a ferrofluid and a non-magnetic fluid between two parallel vertical flat plates, under the influence of an external magnetic field applied by a permanent magnet arbi...
Article
Full-text available
The motion of a spherical bubble in a ferrofluid subjected to an acoustic pressure field and a magnetic field is examined. The continuous fluid here is a colloidal suspension composed of ferromagnetic particles dispersed in a Newtonian carrier liquid. The constitutive equation for the fluid is based on the standard Maxwell tensor for a symmetric or...
Article
Full-text available
This work presents theoretical and experimental analyses on the kinematics-wave motion of suspended active particles in a biological fluid. The fluid is an active suspension of nematodes immersed in a gel-like biological structure, moving at a low Reynolds number. The nematode chosen for the study is Caenorhabditis elegans. Its motion is subjected...
Article
This work explores the physics of an ordered set of interacting spheres immersed in a carrier liquid. We present numerical simulations that compute the translational and rotational motion of NN interacting spheres based on classical principles of Stokesian dynamics. The spheres are assumed to be made of a magnetizable material, subjected to magneti...
Article
This work explores, from a numerical perspective, the role of particle rotational inertia on the magnetization dynamics of ferrofluids. A robust numerical method is used for this purpose. The numerical research code is based on the use of a convergent long range dipolar interactions technique. These interactions are computed through a sophisticated...
Poster
Full-text available
Poster presented at the CILAMCE 2016 – XXXVII Ibero-Latin American Congress on Computational Methods in Engineering by my undergraduate student Késsia Tayná. She is currently doing a scientific initiation program under my supervision.
Conference Paper
Full-text available
In this work we use computational tools to model a monodisperse diluted colloidal suspension of permanently magnetized nanoparticles in carrier liquids that do not present magnetic properties. Three models are used to simulate repulsive forces acting on the particles, namely, the Screened-Coulomb potential based repulsive force, the classic Lennard...
Poster
Full-text available
Poster presented at the UnB Scientific Initiation congress by my former undergraduate student Arthur Campos.
Article
This work focuses on a theoretical investigation of the shape and equilibrium height of a magnetic liquid–liquid interface formed between two vertical flat plates in response to vertical magnetic fields. The formulation is based on an extension of the so called Young–Laplace equation for an incompressible magnetic fluid forming a two-dimensional fr...
Article
Full-text available
The main goal of this article is to study the oscillatory motion of a spherical gas bubble immersed in a Newtonian liquid subjected to a harmonic pressure excitation. We use the classical Rayleigh-Plesset equation to study the radial motion of the bubble undergoing a forcing acoustic pressure field. The second order nonlinear ordinary differential...
Poster
Full-text available
Poster presented by my undergraduate student, Ciro Fraga Alegretti, in the 3rd International Conference on Nanoscience, Nanotechnology and Nanobiotechnology.
Conference Paper
Full-text available
The main goal of this article is to identify the vibrational patterns of an oscillating spherical bubble immersed in a ferrofluid using Neural Networks. The gas bubble is immersed on a magnetic fluid and subjected to an harmonic pressure excitation and an applied magnetic field. The classical Rayleigh-Plesset equation is modified and a magnetic ver...
Conference Paper
Full-text available
This work explores the sedimentation process of an approximately initially spherical blob of dense particles immersed in a Newtonian fluid. We develop an experimental and numerical approach. For our experiments we designed a sedimentation column with super high viscosity silicon oil as the surrounding fluid. The particles are made of iron and sedim...
Article
Full-text available
This work presents analytic and numerical results for a unidirectional flow in a circular capillary of a magnetic fluid. A condition that deviates from the standard equation of equilibrium magnetization due to the vorticity of the flow is considered. We show that the model of a magnetic symmetrical fluid with no-coupling between magnetization and f...
Research
Full-text available
Accepted for presentation and publication on 23rd ABCM International Congress of Mechanical Engineering - December - 2015
Research
Full-text available
Accepted for presentation and publication on 23rd ABCM International Congress of Mechanical Engineering - December - 2015
Research
Full-text available
Accepted for presentation and publication on 23rd ABCM International Congress of Mechanical Engineering - December - 2015
Presentation
Full-text available
PDF slides from the lecture I gave on the award cerimony of the ABCM PhD Thesis Prize in 2014. The videos presented on the slides can be seen at the link: https://www.youtube.com/user/rafaelgabler/videos?view=0&sort=dd&shelf_id=0
Article
Full-text available
A new optimization algorithm based on a minimum residual technique is introduced to reduce the instability of numerical methods due to using wall functions to specify the boundary conditions for high Reynolds number flows. In the present article, four different models of the wall-function approximation are investigated for separated flow inside a t...
Article
Full-text available
We study the relative trajectories of two magnetic spheres interacting in a dilute suspension in the presence of particle inertia and Brownian motion effect. The particles settle relative to one another under the action of gravity and when in close contact they exert on each other a magnetic force and torque due to a permanent magnetization. The ba...
Article
Full-text available
The goal of this work is to propose a new methodology to simulate turbulent thermal wall flows using the classical κ − ε model. The focus of this approach is based on the manner used to implement heat flux boundary conditions on the solid walls. In order to explain and to validate this new algorithm, several test cases are presented, testing a grea...
Conference Paper
Full-text available
The use of classical analogies between turbulent heat and momentum diffusion, employed to estimate the wall heat transfer rates in turbulent wall flows, is numerically modelated in this work. Some approaches are proposed in order to quantify the heat transfer rates in recirculation regions of turbulent flows and an algorithm, used to impose heat fl...
Conference Paper
Full-text available
This works shows how some technicalities in the design of the diffuser can affect the turbulent boundary layer detachment. The behavior of a turbulent flow of air, inside a two dimensional asymmetric straight-walled diffuser, with an divergence angle of 9.97 degrees, is numerically simulated considering some aspects of the solid boundary geometry....
Conference Paper
Full-text available
The temperature and velocity fields, for two turbulent flows generated by natural convection were investigated by numerical simulation. The analyzed flows are the natural convection provided by a heated vertical flat plate and the natural convection inside a tall cavity with side walls in different temperatures. The numerical algorithm applies a co...
Article
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2009. O presente trabalho é um estudo numérico sobre o emprego de analogias entre difusão turbulenta de quantidade de movimento e de calor como metodologia para imposição de condição de contorno de fluxo de calor em escoamentos de camada l...

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Projects

Projects (5)
Archived project
This project aims to explore the nonlinear oscillating motion of a spherical bubble immersed in both Newtonian and non-Newtonian fluids. The idea of exciting a nonlinear system with an harmonic force field and to observe its response in time and frequency domains is to understand how individual mechanisms of this bubble-liquid interaction affect the nonlinear response of the bubble. We are now exploring this problem in the context of FHD, where a small gas bubble is inserted in a magnetic liquid and excited with an acoustic harmonic field together with an applied magnetic field.
Project
To explore, both numerically and experimentally, some systems of technological interest where the increase of heat transfer rates in turbulent flows is desired.