Members

IMMC

Miltiadis Papalexandris
Professor
Contact - Personnal web page
Recent publications

received an MSc degree in Naval Architecture & Marine Engineering from the National Technical University of Athens and MSc and PhD degrees in Aeronautics from the California Institute of Technology (Caltech). Soon after the completion of his PhD, he joined the Engineering Staff of NASA's Jet Propulsion Laboratory. While at NASA, he worked mainly on thermal control and optical modeling of space telescopes, including the James Webb Space Telescope (JWST) and the Laser Interferometry Space Antenna (LISA). In 2002 he became a member of the academic personnel (faculty) at UCL where he remains until now. He is the recipient of the William Balhaus Dissertation Prize of Caltech, NASA's Space Act Award, and the NOVA Award of Excellence of NASA. Prof. Papalexandris is an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA).
The research activities of his group lie primarily on the fields of Theoretical and Computational Fluid Dynamics with particular emphasis on the fundamentals of multi-phase flows, complex fluids, reacting flows, and electrohydrodynamics. These activities cover: i) development of mathematical models for the flows of interest, ii) algorithm development and implementation for these models, iii) software verification and validation, and iv) detailed numerical studies and simulations via high performance computing.

IMMC main research direction(s):
Computational science
Energy
Fluid mechanics

Keywords:
non-equilibrium thermodynamics
reacting flows
two-phase flows

Research group(s): TFL

PhD and Post-doc researchers under my supervision:


Numerical Modeling and Simulation of Sediment Mobilisation and Transport due to Turbulent Currents
Anouk Riffard

The proposed doctoral research evolves around two principal axes. The first one is the development of mathematical models and algorithms for flows of fluid-solid particles mixtures, i.e. granular suspensions. The second one is the use of these algorithms for the study of sediment mobilisation and transport due to turbulent currents.


Electric charge generation and transport in turbulent flows
Mathieu Calero

The general objective of this thesis is to advance the state-of-the-art in the mathematical modelling and numerical simulation of turbulent flows involving electrically charged fluids. The specific goals of the proposed research are the following. Firstly, the development of efficient numerical methodologies and related parallel computer codes for the prediction of electric charge transport in turbulent flows. Secondly,the development of a computational model for charge generation at fluid – solid wall interfaces. Then, the study of electric charge generation and transport in real-life industrial turbulent flows via numerical simulations, and comparisons with experiments. Finally, based on the findings, the improvement of safety for flows of electrically charged fluids that are used in the process industries.


Natural convection and boiling in domains with immersed porous structures subjected to internal heating
Victoria Hamtiaux

My doctoral research propose to advance the state-of-the-art in the modelling and simulation of natural convection in domains with immersed porous structures. Such flows are encountered in numerous natural phenomena (wind through urban areas, forest fires, and others) and technological applications (rapid heat-transfer devices, spent-fuel pools of nuclear power stations etc.) The motivation for my study comes from the need for improved understanding of convection and boiling phenomena that occur during a Loss of Cooling Accident (LOCA) in spent fuel pools of nuclear power stations; with this regard, the storage racks of used fuel are macroscopically modeled as a porous medium.
Concerning the model, the solid matrix and the fluid are modeled as two distinct continuous media. A single-domain approach is used, i.e. a single set of equations is employed for the fluid that is valid in both porous and pure-fluid subdomains. The model also considers the phase change of water.


Modelling and simulation of turbulent thermal convection at high Rayleigh numbers
Louis Alsteens

The research project focuses on improving the understanding of the natural convection phenomena in nuclear spent fuel pools in case of a loss of cooling accident. The turbulent convection will be studied via different numerical simulations such as the simulation of turbulent convection at high Rayleigh number. The final goal is the simulation of turbulent convection in a liquid-gas system.


Modelling and simulation of turbulent convection with intense phase change
Julien Carlier

I work on the modeling and programming of two-phase flow methods to study the coupled effect of the natural turbulent thermal convection at the material interface between the stored water in spent fuel pools and the air-vapor mixture of the surrounding atmosphere.


Development of new modelling approaches and robust numerical methods for the simulation of spray combustion of alternative fuels and biofuels
Alice Ponet

This doctoral thesis project concerns the development of new modelling approaches and robust numerical methods for the simulation of spray combustion of alternative fuels and biofuels, such as biodiesel and ethanol. Further, this research involves detailed numerical simulations of the flows of interest under realistic engine conditions. Particular emphasis will be paid to the accurate prediction of the breakup and evaporation of fuel droplets, the interaction between the flow turbulence and the combustion process and the formation of pollutants such as soot.



Recent publications

See complete list of publications

Journal Articles


1. Sula, Constantin; Grosshans, Holger; Papalexandris, Miltiadis. Numerical study of spray combustion of a biodiesel surrogate fuel using the LES-FGM approach. In: Combustion and Flame, Vol. 249, no.C, p. 112611 (2023). http://hdl.handle.net/2078.1/269356

2. Sula, Constantin; Grosshans, Holger; Papalexandris, Miltiadis. Large‐Eddy Simulations of Spray A Flames Using Explicit Coupling of the Energy Equation with the FGM Database. In: Flow, Turbulence and Combustion, Vol. 109, no., p. 193-223 (2022). doi:10.1007/s10494-022-00320-2. http://hdl.handle.net/2078.1/260950

3. Calero, Mathieu; Grosshans, Holger; Papalexandris, Miltiadis. A computational framework for electrification of liquid flows. In: Journal of Loss Prevention in the Process Industries, Vol. 74, no.c, p. 104637 (2021). doi:10.1016/j.jlp.2021.104637. http://hdl.handle.net/2078.1/250811

4. Marichal, Joauma; Papalexandris, Miltiadis. On the dynamics of the large scale circulation in turbulent convection with a free-slip upper boundary. In: International Journal of Heat and Mass Transfer, Vol. 183, no.C, p. 122220 (2022). doi:10.1016/j.ijheatmasstransfer.2021.122220. http://hdl.handle.net/2078.1/254590

5. Varsakelis, Christos; Gelbgras, Valérie; Papalexandris, Miltiadis. On the wall boundary condition for the velocity in concentrated suspensions. In: Journal of Non-Newtonian Fluid Mechanics, Vol. 305, no., p. 104830 (2022). doi:10.1016/j.jnnfm.2022.104830. http://hdl.handle.net/2078.1/260901

6. Riffard, Anouk; Papalexandris, Miltiadis. Numerical study of the collapse of columns of sand immersed in water using two-phase flow modeling. In: International Journal of Multiphase Flow, Vol. 153, p. 104143 (2022). http://hdl.handle.net/2078.1/261158

7. Papalexandris, Miltiadis. Attenuation of gaseous detonations by porous media of fine microstructure. In: Combustion and Flame, Vol. 232, no., p. 111518 (2021). doi:10.1016/j.combustflame.2021.111518. http://hdl.handle.net/2078.1/247972

8. Hay, William Andrew; Martin, Jimmy; Migot, Benoît; Papalexandris, Miltiadis. Turbulent thermal convection driven by free-surface evaporation in cuboidal domains of different aspect ratios. In: Physics of Fluids, Vol. 33, no.1, p. 015104 (2021). doi:10.1063/5.0035277. http://hdl.handle.net/2078.1/240330

9. Grosshans, Holger; Bissinger, Claus; Calero, Mathieu; Papalexandris, Miltiadis. The effect of electrostatic charges on particle-laden duct flows. In: Journal of Fluid Mechanics, Vol. 909, no., p. A21 (2021). doi:10.1017/jfm.2020.956. http://hdl.handle.net/2078.1/240331

10. Varsakelis, Christos; Papalexandris, Miltiadis. Bridging the gap between the Darcy- Brinkman equations and the Nielsen model for tortuosity in polymer-filled systems. In: Chemical Engineering Science, Vol. 213, p. #115394 (2020). http://hdl.handle.net/2078.1/223098


Conference Papers


1. Marichal, Joauma; Papalexandris, Miltiadis. Numerical simulations of evaporation driven turbulent convection driven by a descending free surface. 2022 xxx. http://hdl.handle.net/2078.1/264847

2. Calero, Mathieu; Papalexandris, Miltiadis. Electric charge generation and transport in turbulent wall bounded flows. 2022 xxx. http://hdl.handle.net/2078.1/264838

3. Carlier, Julien; Papalexandris, Miltiadis. An efficient interface-tracking method for evaporative surfaces. 2022 xxx. http://hdl.handle.net/2078.1/264842

4. Hamtiaux, Victoria; Papalexandris, Miltiadis. Numerical Simulations of turbulent thermal convection in a domain composed of a pure-fluid region and an immersed heated porous medium. 2022 xxx. http://hdl.handle.net/2078.1/264839

5. Alsteens, Louis; Papalexandris, Miltiadis. Wall modelled Large Eddy Simulation of natural convection at high Rayleigh number. 2022 xxx. http://hdl.handle.net/2078.1/264844

6. Sula, Constantin; Grosshans, Holger; Papalexandris, Miltiadis. Large Eddy Simulations of spray flames of biodiesel surrogate. 2022 xxx. http://hdl.handle.net/2078.1/264884

7. Riffard, Anouk; Papalexandris, Miltiadis. Influence of the grain size and the fluid viscosity on the collapse of submerged sand columns. 2022 xxx. http://hdl.handle.net/2078.1/264845

8. Marichal, Joauma; Papalexandris, Miltiadis. Numerical study of flow reorientations in turbulent convection with a free-slip upper boundary. In: Proceedings of the 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH19), American Nuclear Society, 2022, 9789076971261 xxx. http://hdl.handle.net/2078.1/258342

9. Hamtiaux, Victoria; Papalexandris, Miltiadis. Numerical simulation of thermal convection over anfd through an internally heat porous medium. In: Proceedings of the 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics NURETH19, American Nuclear Society, 2022, 9789076971261 xxx. http://hdl.handle.net/2078.1/258344

10. Riffard, Anouk; Papalexandris, Miltiadis. Collapse of submerged sand columns: the role of the grain diameter and the fluid viscosity. In: Proceedings of the 37th International Conference on Coastal Engineering, American Society of Civil Engineers, 2022, 978-0-9896611-4-0 xxx. http://hdl.handle.net/2078.1/266058


Books


1. Papalexandris, Miltiadis. Gas Dynamics. Presses Universitaire de Louvain: Louvain-la-Neuve, Belgium, 2022. 978-2-39061-281-0. 239 pages. http://hdl.handle.net/2078.1/265983

2. Papalexandris, Miltiadis. Combustion and Fuels. Presses Universitaires de Louvain: Louvain-la-Neuve, 2020. 978-2-87558-979-8; 978-2-87558-980-4. 188 pages. http://hdl.handle.net/2078.1/191232

3. Papalexandris, Miltiadis. Unsplit numerical schemes for hyperbolic systems of conservation laws with source terms. 1997. 978-0-591-49445-7. 148 pages. http://hdl.handle.net/2078.1/70733