# Francesc Xavier GrauUniversitat Rovira i Virgili | URV · Department of Mechanical Engineering

Francesc Xavier Grau

Prof. Fluid Mechanics

## About

113

Publications

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1,049

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Introduction

Additional affiliations

August 2001 - present

January 1992 - July 2001

January 1991 - present

Education

January 1983 - September 1986

September 1976 - June 1981

## Publications

Publications (113)

We employ three-dimensional, fully resolved numerical simulations using the volume-of-fluid method to study the motion and interaction of two in-line bubbles ascending in both Newtonian and shear-thinning fluids. Additionally, we explore passive scalar transfer between the fluid phases across a variety of fluidic conditions, modeling shear-thinning...

The transient natural convection of variable and constant viscosity fluids in a side cooled cubical cavity is studied experimentally. The convective flow in the cavity is visualized by the shadowgraph technique. The fluid was initially preheated and enough time is allowed to assure uniform temperature distribution. Temperature difference is introdu...

In this paper, we analyse the flow in a cylindrical cavity of aspect ratio H / R = 2, with a top lid rotating with a sinusoidal time-varying speed. The Reynolds numbers, based on the time-averaged rotating speed and the radius of the cavity (Re = $$ \Omega _0 R^2/\nu $$ Ω 0 R 2 / ν ) are 2800, 3500 and 4100. Particle Image velocimetry measurements...

The scalar transfer rate from a bubble to a quiescent fluid with Carreau rheological behavior is studied here with Bond and Galilei number values respectively equal to 30 and 2 and a non-dimensional inelastic time constant (λ) equal to 6. Under these conditions the bubble dynamics regime stays within the steady and oscillatory areas. Navier Stokes...

In this work, several studies of aging pipes have been compiled and, starting on the basis of circulating flow through a pipe of t years of age is based on the inner diameter and driving age, some design life tables have been made corresponding to the main materials and components of pipes specifically: iron, steel, concrete, fibre cement and plast...

In this work Euler-Euler Large Eddy Simulations (LES) of dispersed turbulent gas–liquid flows in a cylindrical bubble column are presented. Besides, predictions are compared with experimental data from Vial et al. 2000 using laser Doppler velocimetry (LDV). Two test cases are considered where vortical-spiral and turbulent flow regimes occur. The su...

Hace dos años, la consellera d'Empresa i Coneixement del Govern de la Generalitat de Catalunya, Àngels Chacón, me hizo el honor de confiar en mí al frente de la Secretaría de Universidades e Investigación. Uno de los encargos que me hizo fue el de retomar los trabajos del incipiente Pacto Nacional por la Universidad. Rápidamente nos pusimos de acue...

This paper analyses the local and time-dependent behavior of large-scale structures responsible for liquid circulation in gas-water flow of a 3-D cylindrical bubble column of high aspect ratio with a multiple orifice for uniform aeration. The large-scale flow structures play an important role in the mixing and the mass transfer while coherent struc...

This contribution analyzes the evolution of the higher education and doctorate in Europe and Spain in the last decades, and its relationship with the evolution of the economy based on knowledge. It also analyzes the strong impact that doctorate has on the research activity and the tensions between the Bologna process, that is collaborative, harmoni...

The study of the dual responsibilities of universities at local and global level has been the objective of this 6th HEIW GUNI Report on “Towards a Socially Responsible Higher Education Institution; globally and locally engaged”. In this final chapter, the editorial team makes a joint reflection from all the contributions and give a set of recommend...

Towards a Socially Responsible University: Balancing the Global with the Local aims to analyse the dual responsibilities of universities at local and global level, exploring the potential conflicts and intrinsic difficulties in addressing both the local demands of society based on the race for global competitiveness and the local and global demands...

Towards a Socially Responsible University: Balancing the Global with the Local aims to analyse the dual responsibilities of universities at local and global level, exploring the potential conflicts and intrinsic difficulties in addressing both the local demands of society based on the race for global competitiveness and the local and global demands...

Oppinion article, published in FET a Tarragona (november, 2016), describing the characteristics, capacities and strenghts of Tarragona to become a region of knowledge

Spanish translation from the opinion article " Sobre monuments " published in the newspaper Diari de Tarragona, 9 June 2016.

This document stems from a previous publication: “¿Cómo están las universidades españolas en los rankings? La visión académica: La preponderancia del impacto científico en los rankingsde universidades” (“Where do Spanish universities stand in the rankings? The academic vision: The preponderance of scientific impact in university rankings”), include...

This paper deals with the dual responsibilities of universities at local and global scale, exploring the potential conflict, or intrinsic difficulties, in addressing both local demands of society based on the race for global competitiveness and local and global demands to contribute to a more equitable and sustainable society (at local and global s...

Autores: Vicent Climent (Editor) Francesc Michavila (Editor) María Ripollés (Editor) Vicent Climent (Autor/a) Francesc Michavila (Autor/a) María Ripollés (Autor/a) Pilar Álvarez (Autor/a) Enric Banda (Autor/a) Mónica Bragado (Autor/a) Angelina Costa (Autor/a) Urbain Ben De Winter (Autor/a) Pilar García-Agustín (Autor/a) Xavier Grau (Autor/a) Federi...

Scientific impact is the main and most determinant factor in the position of a university in rankings. This study shows also how impact and rankings can be used for a better knowledge of the lvel of quality of university systems

The Universitat Rovira i Virgili (URV) based in Tarragona can serve as an example of how to embed the concept of social innovation into the curricula. Through the so-called “Market of Social Projects”, an activity organized in the context of its Service Learning Program, URV promotes direct contact between local communities, faculty and students in...

Opinion article published in the catalan newspaper Diari de Tarragona

Opinion article in the spanish newspaper El País (15/12/2014), answering the following specific question from the journalist: "Based in their position in rankings, are the spanish universities mediocre?"

Opinion article in the catalan newspaper ARA

Higher Education of the World 5 is the 5th report made by GUNI (Global University Network for Innovation). In this occasion, devoted to Knowledge, Engagement & Higher Education: Contributing to Social Change

Participación en la Mesa 5: Universidad y Entorno Social

Numerical simulations of the isothermal two-phase flow distribution in the packed bed of a reactor used for fuel hydrodesulfurization using the commercial software Fluent are reported. As a first step, the heat and mass transfer as well as the chemical reactions are not taken into account. The reactor considered has, above the bed, a distribution t...

In this study, we propose a simple formula to calculate the steady-state surface averaged Sherwood number at high Schmidt numbers when a first-order chemical reaction occurs on a wall. The formula uses the surface averaged Sherwood number corresponding to the mass transfer rate with an infinitely fast kinetic and the Damkhöler number. The validity...

Opinion article published in the spanish newspaper, El País

Open-ended cavity 16 Stability 17 Laminar mixed convective flow over a three-dimensional open cavity with heating from below at constant tem-18 perature was numerically simulated using direct numerical simulation and the most hydrodynamic and thermal 19 aspects of the flow are presented. The effects over the velocity and temperature distribution of...

The aim of the book is to present the author’s proposals on the reform of the governance model from a holistic and functional perspective. The first task when designing a system of governance should be to identify the function that it is to fulfil, which leads on to the question of exactly why universities are meant to be autonomous. For the good o...

El presente documento pretende exponer las propuestas del autor sobre la reforma del modelo de gobernanza a partir de una aproximación holística y funcional. El punto de partida para diseñar un sistema de gobernanza debería ser la identificación de la función que debe cumplir, lo que remite al porqué de la definición de la autonomía universitaria....

In this study we present, analyze and compare the power spectral density of the wall shear stress in
a turbulent plane channel flow obtained with different techniques. Experimentally the instantaneous wall
shear stress was measured with the electrochemical technique using different probes, which give approxi�
mately the same results after applying...

In this work, an experimental investigation of the single- and multiphase flows of two sets of fluids, CO2–ethanol and CO2–methanol, in a non-adiabatic microfluidic T-junction is presented. The operating conditions ranged from 7 to 18 MPa, and from 294 to 474 K. The feed mass fraction of CO2 in the mixtures was 0.95 and 0.87, respectively. Under th...

In this study the turbulent mixing in a model of a polymerization reactor is analyzed experimentally and
numerically. The model corresponds to a zone of an autoclave reactor equipped with a stirrer. Two
different configurations of the stirrer, with different arrangement of the paddles, have been considered.
The mixing process has been monitored by...

This work presents a numerical analysis of the effects of thermal boundary conditions, fluid variable viscosity and wall conduction on transient laminar natural convection of a high Prandtl number (Pr=4×104) fluid (Golden Syrup) in a cubical cavity. The simulations consider physical situations realizable at laboratory scale using a cavity with Plex...

Opinion article published in the spanish newspaper El Periódico, in June, 29, 2011

a b s t r a c t Direct numerical simulations of particle dispersion in the turbulent natural convection flow between two vertical walls kept at constant but different temperatures are reported. It is assumed that the particles do not affect the flow (i.e. the dilute phase approximation is adopted). Particles with different levels of inertia, or Sto...

The transient natural convection of variable and constant viscosity fluids in a side cooled cubical cavity is studied experimentally. The convective flow in the cavity is visualized by the shadowgraph technique. The fluid was initially preheated and enough time is allowed to assure uniform temperature distribution. Temperature difference is introdu...

Analysis of the Spanish Public University System

We report numerical simulations of forced convection heat transfer rates of a steady laminar flow in a two-dimensional model of porous media to elucidate the differences observed between the numerical predictions of Kuwahara et al. (2001) [Int. J Heat Mass Trans. 44, 1153–1159] and Gamrat et al. (2008) [Int. J Heat Mass Trans. 51, 853–864]. A modif...

a b s t r a c t A numerical study has been carried out to analyze the effects of mixed convective flow over a three-dimensional cavity that lies at the bottom of a horizontal channel. The vertical walls of the cavity are iso-thermal and all other walls are adiabatic. The cavity is assumed to be cubic in geometry and the flow is laminar and incompre...

Using a typical shear cell arrangement, the degree of accuracy attained in the determination of the interdiffusion coefficients at low and moderate thermal and solutal Rayleigh numbers is analyzed here. It is concluded that, despite the marked directionality of these Fickian processes, thermal convective contamination is always negligible in real e...

a b s t r a c t We analyzed a database of a direct numerical simulation of natural convection in a vertical channel. The flow is driven by a constant temperature difference imposed at the walls (Ra = 5.4 Â 10 5 , Pr = 0.7). The averaged flow and turbulent statistics are in good agreement with previous direct numerical simulations reported in the li...

We simulated steady and unsteady natural convection flows of a nanofluid in a square cavity. If the particle distribution is perfectly uniform there is a reduction of the heat transfer rates of about 1% in comparison with those corresponding to the pure liquid. The Lagrangian tracking of the particles shows that there is no preferential concentrati...

We analyze numerical simulations of a second-order chemical reaction (Da = 1) in a fully developed turbulent plane channel flow at a low Reynolds number (Reτ = 180). The reactive plume is formed when a reactant A is released through a line source into the channel flow doped with reactant B. Two different inlet pre-mixing conditions and line source...

a b s t r a c t In this paper, we analyze the influence of aiding and opposing buoyancy on the statistics of the wall transfer rates in a mixed convection turbulent flow at low Reynolds numbers in a vertical plane channel. The analysis is carried out using a database obtained from direct numerical simulations performed with a second-order finite vo...

Direct numerical simulations of the turbulent dispersion of a buoyant line of hot fluid released at the inlet of a plane channel flow are reported (Reτ = 180, Gr = 107 and Pr = 0.7). Results of turbulent dispersion of a neutrally buoyant scalar and mixed convection flow are also included. The buoyancy force induces a vertical movement that, althoug...

The transient laminar natural convection and conduction of high Prandtl number (Pr = 1.9 × 104) fluid with variable viscosity in a cavity bounded with massive walls is numerically studied. Initially the fluid in the
cavity is considered to be at rest at constant temperature and the temperature of the six walls is set to constant value through
the c...

This work presents numerical analysis of effects of thermal boundary conditions, fluid variable viscosity and wall conduction
on transient laminar natural convection of high Prandtl number (Pr = 104) fluid (Golden Syrup) in a cubical cavity. The simulations consider the flow in a cavity with Plexiglas walls of 1cm of thickness, the inside dimension...

We analyzed numerically the frequency response of the mass transfer rates produced at the surface of an electrochemical probe to the fluctuations of the wall shear stress obtained from a direct numerical simulation of a turbulent plane channel flow at Reτ = 150. At low and high frequencies the response to the turbulent wall shear stress is in accor...

The White Paper on the University of Catalonia offers a structure for a common framework for Catalan public universities to build a collective and cooperative strategy to position the Catalan university system as a role model for southern Europe. The paper offers 64 strategies and 73 specific projects to be implemented in order to build this univer...

El Libro Blanco de la Universidad de Cataluña es la configuración de una hoja de ruta común de las universidades públicas catalanas para construir una estrategia colectiva y cooperativa que sirva para situar Cataluña como espacio universitario de referencia en el sud de Europa. El libro propone 64 estrategias y 73 proyectos concretos que se quieren...

El Llibre Blanc de la Universitat de Catalunya és la configuració d’un full de ruta comú de les universitats públiques catalanes per construir una estratègia col·lectiva i cooperativa que serveixi per situar Catalunya com a espai universitari de referència al sud d’Europa. El llibre proposa 64 estratègies i 73 projectes concrets que es volen desple...

Let v→=v→(p,t) be the velocity field of a Newtonian fluid, ω→=ω→(p,t) its vorticity field and (eij) its 2-covariant rate-of-strain tensor. In this paper we give a formulation to identify boundary planes in analytical and numerical three-dimensional flow fields. The proposed formulation is based on the calculation of the locus where ∑i,j=13viωjeij=0...

Experimental measurements and numerical simulations of natural convection in a cubical cavity heated from below and cooled from above are reported at turbulent Rayleigh numbers using water as a convective fluid (Pr = 6.0). Direct numerical simulations were carried out considering the Boussinesq approximation with a second-order finite volume code (...

In this paper we analyze the flow structures responsible for large local instantaneous deviations of the conventional momentum–heat transfer analogy and large fluctuations of the wall shear stress and the wall heat flux in a forced convection turbulent channel flow at low-Reynolds numbers (Re = 4570, Pr = 0.7). The analysis was carried out using a...

This paper presents and discusses the numerical simulations of transient laminar natural convection cooling of high Prandtl number fluids in cubical cavities, in which the six walls of the cavity are subjected to a step change in temperature. The effect of the fluid Prandtl number on the heat transfer coefficient is studied for three different flui...

This paper presents and discusses numerical simulations of forced convection heat transfer in a rotating square duct at high rotation rates. The mean pressure gradient has been kept constant in the simulations that were conducted with a second order finite volume code with a dynamical localized subgrid scale model. The rotation number based on the...

The impact of the gravity, constant and g-jitter, as well as the shearing process on the determination of the diffusion coefficient has been analyzed here computationally using a twenty segments shear cell and two generic liquid systems in the range of molten semiconductors and liquid metals under isothermal conditions. As a result of this prelimin...

Two-phase flow distribution in a trickle-bed reactor used for fuel hydrodesulfuration has been simulated using the commercial finite volume code Fluent. After checking the performance and modelization capabilities of the different models available in the code, a three-phase model was chosen, considering the particles of catalyst as a granular stati...

The effects of a non-Boussinesq fluid are discussed for Rayleigh-Bénard convection in a cubical cavity with perfectly conducting side walls at low and high Rayleigh numbers using water as a convecting fluid. Non-Boussinesq simulations were calculated with a variation of 62% and 40% of the thermal expansion coefficient and viscosity, respectively, b...

In this paper we analyze the spatial distribution of the instantaneous departures from the conventional analogy between momentum and heat transfer of a pressure driven fully developed turbulent channel flow at low Reynolds numbers (Re=4570, Pr=0.7). The analysis was carried out using a database obtained from a direct numerical simulation performed...

The present work deals with the natural convection flow and heat transfer from a horizontal plate cooled from above. Experiments are carried out for rectangular plates having aspect ratios between φ=0.036 and 0.43 and Rayleigh numbers in the range 290⩽Raw⩽3.3×105. These values of Raw and φ have been selected below those commonly considered in previ...

A new technique for the construction of orthogonal grids around convex bodies is presented. The method, which is analytical or numerical depending on how the body boundary is expressed, is based on the development of geometric foliations that follow a prescribed direction (for instance, the prevailing direction of flow) around convex bodies of arbi...

The lid-driven incompressible flow in a toroidally shaped cavity of square cross-section (dd) and radius of curvature r c is studied. For discrete values of the curvature ratio (d/r c), the Reynolds number at which the flow becomes three-dimensional (Re c) is determined by means of linear stability analysis. Present results show that both Re c and...

This paper discusses flow structures and heat transfer rates generated by Rayleigh–Bénard convective motions of a Boussinesq fluid with a Prandtl number of 0.7 in a perfectly conducting cubical cavity. Complete numerical simulations of laminar flows were conducted in the range of Rayleigh numbers 7×103⩽Ra⩽105. The large-eddy simulation (LES) techni...

Rayleigh-Bénard convection in a cubical cavity with adiabatic or conductive sidewalls is experimentally analyzed at moderate
Rayleigh numbers (Ra ≤ 8 × 104) using silicone oil (Pr=130) as the convecting fluid. Under these conditions the flow is steady and laminar. Three single-roll-type structures and
an unstable toroidal roll have been observed in...

Numerical simulations of flow in a rotating square duct at high rotation rates are presented. Computation and analysis of the different terms of the averaged momentum budget near the sidewalls have shown the dominant mechanisms of momentum transfer in these regions. A model for the velocities has been developed by analytically solving simplified ve...

Horizontal and vertical integration of engineering education is achieved through an early-design project where students get ac-quainted with Total Quality Management (TQM) principles and design processes from year-one of their University educa-tion. The project is embedded in the undergraduate chemical engineering curriculum as an activity that inv...