Ongoing research projects

IMMC

Ongoing research projects in iMMC (September 2020)


This a short description of research projects which are presently under progress in iMMC.
Hereunder, you may select one research direction or choose to apply another filter:

Biomedical engineering

Computational science

Civil and environmental engineering

Dynamical and electromechanical systems

Energy

Fluid mechanics

Processing and characterisation of materials

Chemical engineering

Solid mechanics


Research direction:
Listed keyword:
Other keyword:
Division:
Supervisor:

List of projects related to: Computational science




WholeTrack
Researcher: Nicolas Docquier
Supervisor(s): Paul Fisette

The project aims at improving railway track lifecycle by improving its components such as the ballast, the sleeper, elastic pads, ... It consists in developing computer models coupling multi-body system dynamics (MBS) and granular modelling method (the discrete element method, DEM). Full scale experiments are conducted in parallel to validate the numerical models and assess the developed solutions.



Development of high-toughness cryogenic alloys
Researcher: Alvise Miotti Bettanini
Supervisor(s): Pascal Jacques

Materials that can perform at extremely low temperatures are in great demand. Applications span from tanks and pressure vessels for LNG (Liquefied Natural Gas) carriers to structural materials in extreme conditions, like the upcoming exploration of Mars. In this context, it is critical to ensure very high toughness, which measures the resistance to crack propagation, at cryogenic temperatures. In this project, the experimental development of Fe-based superalloys is guided by a CALPHAD-based methodology, which allows the calculation of phase stability and phase transformation with computational models in order to reduce the experimental effort and hasten the development cycle of new materials.



Numerical modelling of estuaries and coastal seas
Researcher: Valentin Vallaeys
Supervisor(s): Eric Deleersnijder

The topic of the research is the numerical modelling of the river-to-sea continuum of major rivers (i.e. Congo River and Columbia River). The goal is to study the estuarine and coastal dynamics and their interactions with tides, river discharges and atmospheric/oceanic circulations. This thesis partly answers the following questions: What is the dynamics of the river-to-sea continuum ? How does the small scale influence the larger one (and vice-versa) ? Can Discontinuous Galerkin methods reduce the numerical dissipation in order to simulate sharp fronts of density and velocity fields ? This thesis is performed within the framework of the SLIM project (http://sites.uclouvain.be/slim/).



Finite strain modelling of polymers and continuous fiber reinforced composites
Researcher: Muralidhar Reddy Gudimetla
Supervisor(s): Issam Doghri

The main thesis goal is to efficiently integrate the constitutive models of resin, fiber and fiber/matrix interface into a mulit-scale approach to predict the behavior of an uni-directional carbon-epoxy composite ply. This would require an efficient constitutive model for the resin/polymer which would address the experimentally observed features like strain-rate, temperature and pressure-dependency. So, an isotropic thermodynamically based fully coupled viscoelastic-viscoplastic model formulated under finite strain transformations was developed considering isothermal conditions, which is further extended to an anisotropic version suitable for structural composites. This model would be implemented in a multi-scale approach, with corresponding models for fiber and fiber/matrix interface, to predict softening/degradation in an uni-directional composite ply.



Implementation of an incompressible hybrid Eulerian-Lagrangian external flow solver
Researcher: Philippe Billuart
Supervisor(s): Grégoire Winckelmans, Philippe Chatelain

Philippe Billuart is working on the development of a new numerical solver that will be able to solve accurately and efficiently any low Mach number external flows. His research is focusing on the hybrid Eulerian-Lagrangian solvers for the incompressible Navier-Stokes equations. Those approaches are based on the decomposition of the computational domain : an Eulerian grid-based solver is used for the computation of the near-wall region, while a Lagrangian vortex method solves the wake region. Even though the coupling of particle methods with Eulerian solvers is not new, only 3D weak coupling were developed so far. This thesis aims to develop a 3D strong coupling ; i.e. a coupling where the Schwarz iterations are not longer required to ensure consistent boundary conditions on each subdomain. As the Schwarz algorithm becomes expensive in 3D, the computational gain in the developed approach should be very significant.



Automatic hexahedral mesh generation for boundary layers
Researcher: Christos Georgiadis
Supervisor(s): Jean-François Remacle

The main objective of our work is to provide with a fast and reliable method for generating boundary layer meshes. We follow a strategy that uses direction fields and a frontal point insertion strategy. The input of our algorithm is an initial triangular mesh of our domain and a direction field calculated on it. The goal is to compute the vertices of the final mesh by an advancing front strategy along the direction field. The final mesh will consists of right angle triangles, optimal for merging into quadrilaterals.



Tidal response of Titan liquid bodies
Researcher: David Vincent
Supervisor(s): Eric Deleersnijder

Titan, a moon of Saturn, has various liquid bodies: surface lakes and seas filled with liquid hydrocarbons and a global subsurface ocean of water.
I numerically studied the tidal flow (see Fig. 1, the tidal ellipses of the first tidal component in Kraken and Ligeia Maria) and motion of the surface lakes and seas by means of SLIM (www.climate.be/slim). The harmonics of the tidal motion (for instance, the tidal range and phase in Kraken and Ligeia Maria, see Fig. 2) and eigenmodes were also studied in order to assess the likelihood of resonance (local or global). Values predicted by the model such as the tidal range and flow of the surface lakes and seas are useful for designing some aspects of the future observation missions.
I am currently modeling the tidal response of Titan's global subsurface ocean by taking into account the solid-fluid interactions with Titan icy crust (see Fig. 3, the sea surface elevation of Titan's ocean with a free top boundary). The dissipation and resonance phenomena will then be studied. The originality of this work lies in the fact that the dynamic tides are taken into account.



A dynamic-based approach for road vehicle design optimization
Researcher: Aubain Verle
Supervisor(s): Paul Fisette, Bruno Dehez

Due to urban zone densification and energy rarefaction, some facets of life habits have to be revised. The mobility doesn’t derogate from this trend and is one of the major future challenges. Automotive industry is developing new solutions to cope with the increasing problem of mobility, the need for energy efficiency and customer requirements. Facing this multiplication of objectives, often conflicting, it is quite unlikely that one particular solution would satisfy all customers in all daily needs as it was with the car until now. Several new kinds of vehicles appear, each of them being able to answer a particular use. In the special case of urban and personal mobility, tilting three-wheelers seem to be a promising solution. Small and agile, they improve the traffic flow while the associated reduction of weight allows better energy efficiency.
Because of the increase – in number and quality – of the criteria imposed to tomorrow’s vehicles, the industry must propose new types of morphologies, incorporate new technologies and detect a maximum of synergies between the latter. Thus we observe a constant increasing design tasks complexity while the development times are shorter than ever. There is a real need for global design methodologies that include, from the earliest stage of the process, a multitude of components among which the dynamics takes place.
This work aims at developing a design methodology especially dedicated to road vehicles. The method has the particularity to enable to manage the trade-off between dynamic performances and mechanical feasibility. The method is being applied to a new three-wheeler under development in our laboratory. The main characteristics of this vehicle are a unipersonal seated position, a narrow track and a electric motorization.
We achieved the design of a first prototype on the basis of the optimization processes. In particular, we develop some very specific mechanical arrangements especially designed to maximize the dynamic performances of the tilting vehicle suspensions. Moreover, it is expected that a first implementation of the prototype will be built in the future to carry out some comparison between experiment and simulation.



Multithreaded Mesh Generation
Researcher: Célestin Marot
Supervisor(s): Jean-François Remacle

The main goal of this thesis is to speedup tetrahedral mesh generation by an order of magnitude. To do so, we are parallelizing and enhancing the whole mesh generation process. Promising results are uncovered at https://www.hextreme.eu/



Curvilinear mesh adaptation
Researcher: Amaury Johnen
Supervisor(s): Jean-François Remacle

graduated as a physician engineer at the University of Liège (Belgium) in 2011. Then he accomplished a PhD in the topic of quadrangular mesh generation and cuvilinear mesh validation, under the supervision of professor Christophe Geuzaine. He started a postdoctoral research in January 2016 under the supervision of professor Jean-François Remacle for working on curvilinear mesh generation, hex-dominant mesh generation and mesh validation.



All-hexahedral meshing
Researcher: Kilian Verhetsel
Supervisor(s): Jean-François Remacle

While there exist algorithms to generate hex-dominant meshes, which contain a majority of hexahedra as well as a mixture of tetrahedra, prisms, and pyramids, automatically generating hexahedral meshes with elements of a reasonable quality is not currently possible. Subdividing the elements of a hex-dominant mesh could allow hexahedral meshes to be generated automatically, but the best known subdivision of a pyramid requires too many elements to be practical (see figure).

My work focuses on finding all-hexahedral meshes of small models such as this pyramid by first finding a topological solution using combinatorial search techniques. A geometric mesh will then be produced by finding coordinates for each vertex in the mesh.



Hextreme
Researcher: François Henrotte
Supervisor(s): Jean-François Remacle

completed his Engineering Degree in 1991 and his PhD in 2000, both at the University of Liège in Belgium. He then spent 4 years at the Katholieke Universiteit Leuven and 6 years at the Institut für Elektrische Maschinen in Aachen, Germany, and is now with the UCL and the ULiège. Developer in the open-source packages Gmsh, GetDP and Onelab, he has also developed skills in the multiphysics simulation of electrical machines and drives. His main interests are finite element analysis, numerical modeling, electromechanical coupling, material properties (hysteresis, iron losses, superconductors), applied mathematics (differential geometry, algebraic topology, convex analysis, dual analysis, energy methods), multiscale methods, sensitivity and optimization.



Poly-cube decomposition of 3D volumes
Researcher: Jovana Jezdimirovic
Supervisor(s): Jean-François Remacle

The aim of the research thesis is to push forward the state-of-the-art of mesh generation and propose for the first time a methodology that allows to automatically create structured multi-block meshes for general 3D domains. For that, an innovative approach that enables automatic decomposition of a general 3D domain into “poly-cubes” is proposed. A “poly-cube” map is a mechanism that allows a seamless parameterization of a 3D domain. The “poly-cube” decomposition provides the multi-block structure that is needed for structured meshing. In order to achieve this goal, the first part of the thesis is dedicated to the development of a “poly-quad” decomposition of a general 2D surface. It is relied on solving adequate Ginzburg Landau equations in order to develop a robust procedure that generates cross fields and locates critical points. Existence and location of critical points – represented as elliptic Fekete points are proved in recent results by Jezdimirovic, 2017. Further, critical points will be connected through the integral lines leading to an automatic decomposition of the domain into “quadrilaterals”. In the next step, the presented idea will be extended to 3D in order to create automatic algorithm for the “poly-cube” decomposition of 3D volumes.



Modelisation and optimization of bird flight
Researcher: Victor Colognesi
Supervisor(s): Philippe Chatelain, Renaud Ronsse

This research project aims at modeling and optimizing bird flight. The goal of this modelization is to get a deep understanding of the mechanisms that govern avian flight and the best way to understand it is to re-create it. That is, the flight will be modeled starting from the given anatomy of a bird and the kinematics will be the result of an optimization process aiming at the most optimal flight.
Compared to other existing studies on the subject of bird flight, this project will follow a "bottom-up" approach, all the way from muscle activation, up to the wing aerodynamics and gait optimization. This approach is necessary to be able to evaluate key values such as metabolic rates, ...
This will allow us to answer a few questions such as :
- What are the mechanisms enabling high efficiency in bird flight ?
- How do we achieve a stable flapping flight ?
This work is purely numerical. The bio-mechanical model of the bird is developed using the multi-body solver Robotran developed at UCL. This bio-mechanical model will be coupled to an aerodynamical model based on a vortex particle-mesh code (VPM) developed at UCL as well.



DNS of reacting particle flows for mesoscale modeling
Researcher: Baptiste Hardy
Supervisor(s): Juray De Wilde, Grégoire Winckelmans

Gas-solid flows are encountered in many natural and industrial phenomena. Fluidized beds are the most well known application of gas-solid reactors in the chemical industry (catalytic cracking, biomass conversion,...).
However, the simulation of such equipments at large scale is still an issue due to the tracking of billions of particles carrying the reaction while interacting with the gas flow. Eulerian-Eulerian models are currently very popular because they describe the solid phase as a continuum, hence drastically lowering the computational cost. Though, these models require closure relations for momentum, heat and mass transfer, often obtained on empirical bases.
The goal of this research is to extract closure laws from Direct Numerical Simulations at particle scale using the Immersed Boundary Method in order to provide new mesoscale models built on physical grounds.



3D crossfield generation for multibloc decomposition
Researcher: Alexandre Chemin
Supervisor(s): Jean-François Remacle

The aim of the project is to realize multibloc decomposition of 3D volumes in order to generate full hex meshes. Nowadays, this kind of decomposition is done by hand. The purpose of this work is to be able to do it in an automatic way. In order to reach this objective, we are generating 3D crossfields in this volume to locate singular points and automatize the decomposition.



RevealFlight
Researcher: Gennaro Vitucci
Supervisor(s): Renaud Ronsse

Currently under investigation is a reductionist model of flight of birds. Main focuses are a neuromuscular control system and fluid-solid interaction at wing level both for a single agent and large flocks.



Automatic quadrilateral and hexahedral meshing
Researcher: Maxence Reberol
Supervisor(s): Jean-François Remacle

My research interests are automatic block decomposition, quadrilateral meshing, hexahedral meshing and robust hex-dominant meshing.



Flight Control and Wake Characterization of Migratory Birds
Researcher: Gianmarco Ducci
Supervisor(s): Renaud Ronsse, Philippe Chatelain

The RevealFlight project aims at shedding light on the efficiency optimization mechanisms deployed by biological flyers, with a specific focus on migratory birds. The efficiency-seeking mechanisms will be sought through the numerical reproduction of flight that includes the morphology, the neuro-muscular configuration and the gait generation. This resulting gait then exploits aerodynamics at the scale of an individual (unsteady lift generation) and at the level of the flock (formation flight). This project thus proposes to synthesize the flight mechanics of birds into a unified framework, combining bio-mechanical, sensory, aerodynamic and social interaction models, in order to reproduce the flying gaits and the interactions within a flock.
A neuro-mechanical model of the birds is currently under development, capturing bio-inspired principles both in the wing bio-mechanics (e.g. structure and compliance) and in its coordinated control (through e.g. a network of coordinated oscillators). The dynamics of this model will be solved by means a multi-body solver and in turn, coupled to a massively parallel flow solver (an implementation of the Vortex Particle-Mesh method) in order to capture the bird’s wake up to the scales of the flock. The study of self-organization phenomena and inter-bird interactions are currently beginning on simple conceptual models, and will be gradually extended to more advanced models developed during the project. It will aim at comparing the efficiency of flocks of selfish flyers with that of flocks in which collaboration takes place, whether implicitly or explicitly.
In my global project picture, the following bottom-up strategy will be adopted:
- Wake characterization: This task studies the wake in terms of the vortex dynamics at play over long distances. The candidate will perform simulations of flying agents in long computational domains in order to capture the wake behavior (topology, instabilities and decay) over longer times and larger scales. This will provide another basis of validation of the project results, given the volume of work on bird wakes;
- Flight stabilization in turbulent or wake-impacted flow: This task aims at the realization of a stabilized flight within a perturbed flow. Two perturbations are envisioned: ambient turbulence and an analytical wake composed of two counter-rotating vortices. Il will Combine previously synthesized gaits and control schemes in order to study the stability of the flyer in a turbulent flow or inside a wake;
- Maneuvers: This task realizes the first maneuvers of the virtual flyer: avoidance and trajectory tracking that will be leveraged in the simulation of multiple flyers that need to interact and swap places. In the present task, this trajectory is still prescribed, in a step towards an autonomous decision-making agent. In order to realize maneuvers, this task implements a control layer above the controllers developed in earlier tasks. Complex maneuvers will be achieved by closing the loop between trajectory errors and the inputs of the lower level controller.



Modèle hybride multi- échelle pour l’ étude rh éologique des solutions de macromolécules
Researcher: Nathan Coppin
Supervisor(s): Vincent Legat

graduated in physical engineering at Université Catholique de Louvain in 2018 and is currently pursuing a PhD under the supervision of Prof. Vincent Legat. The goal of his thesis is to study the performance of the MigFlow Software using applications that require the management of frictional contacts.



Development of high-fidelity numerical methods for the simulation of the aerothermal ablation of space debris during atmospheric entry
Researcher: David Henneaux
Supervisor(s): Philippe Chatelain

This project, lead in collabaration with the von Karman Institute (VKI) and Cenaero, aims at developing high-fidelity numerical methods for the simulation of the aerothermal ablation of space debris during an atmospheric entry.

The number of space debris orbiting the Earth is becoming increasingly problematic for the integrity of operational satellites and the future access to space. The many space debris mitigation projects currently under study require an accurate prediction of the degradation of these objects when they re-enter the atmosphere in order to comply with the severe re-entry safety requirements.

Dedicated engineering softwares are used to assess the survivability of these debris. However, the correlation-based models implemented in these software lack accuracy and they do not allow to gain insight into the complex flow phenomena taking place near the surface of the body, yet essential for the conception of new satellites designed for demise. That is why CFD methods are needed to study this complex situation. But the methods currently available rely on simplifying assumptions that compromise the reliability of the results.

The objective of this project is to develop new high-fidelity numerical methods able to deal with the presence of the three phases in the same domain and their complex interactions. They will be grouped into the ARGO code under development at CENAERO, VKI, and UCL, which relies on the discontinuous Galerkin method. To do so, a highly-accurate multiphase method coupled with evaporation and surface tension models and based on a sharp interface approach will be employed for the treatment of the gas-liquid interface, while a state of the art melting method accounting for the diffuse character of the liquid-solid interface will be considered. Both methods will be built to work with multicomponent compressible equations. The code will then be validated with experimental data from the VKI Plasmatron facility.



Detecting and using locomotion affordances for lower-limb prostheses by active vision
Researcher: Ali Hussein Al-Dabbagh
Supervisor(s): Renaud Ronsse

Healthy lower-limb biomechanics reveals that active prostheses are necessary to provide amputees with human-like dynamics in various locomotion tasks like walking or stair ascending/descending. Ali’s project is about the specific challenges associated to the transition between two of these tasks, where the control parameters of the device has to be smoothly and timely adapted. Active vision is proposed to be used to augment the prosthesis with vision-based detection of possible locomotion affordances, therefore anticipating these transitions as a function of the user’s behavior.