Research

TFL

The research activities in Turbulence and Vortical Flows are led by Profs. G. Winckelmans and P. Chatelain. 

The main methodological contributions of the group concern Computational Fluid Dynamics (CFD) of unsteady vortical and/or turbulent flows at high Reynolds numbers. In particular, the development and validation of high performance methods and their implementation in HPC contexts are achieved: Eulerian methods (spectral, high order finite differences) and hybrid Eulerian-Lagrangian methods (vortex particle-mesh methods (VPM)). They also perform the development and validation of advanced subgrid-scale models including multi-scale models (regularized variational multiscale models (RVMS)) for high fidelity large-eddy simulation (LES) of turbulent flows, including multi-scale models, and also models with proper near-wall behavior (for wall-resolved LES and for wall-modeled LES).
The areas of deployment of these tools cover both fundamental and applied problems in fluid mechanics. They thus cover central issues in fluid mechanics, stability, vortex dynamics, and turbulence but also complex flows such as aircraft wakes, wind turbine aerodynamics and wakes, and CROR systems for propulsion. Other areas of deployment involve bio-propulsion problems and flow control. The group has also been strongly involved with the Cenaero: for helping in its creation and development, and also for research collaborations. In particular, this now concerns the assessment of the discontinuous Galerkin (DG) method for the simulation (DNS and LES) of complex turbulent flows in aerodynamics.

The research in Energy and Thermodynamic Systems is performed by Profs. H. Jeanmart and Y. Bartosiewicz.

Prof. H. Jeanmart performs research activities in biomass, combustion and alternative fuels. The gasification of biomass is studied with a focus on small-scale fixed bed technologies. More specifically, the two-stage concept is developed thanks to a fully automated 200kWth gasification facility including a cleaning unit and an engine. The behaviour of different wastes (sludge, waste wood, railroad ties, etc.) under gasification is the major focus of the on-going research. The combustion of biomass in power plants is also a subject of research using a dedicated pyrolysis model developed for high temperatures and heating rates and a drop tube furnace aimed at studying the fouling propensity of biomass.
Hydrocarbon and oxygenated species kinetic mechanisms are developed thanks to experiments on two low-pressure flat flame burners. The mechanism, called “UCL”, is now composed of 830 reactions and 160 species. It handles species like methane, ethanol, benzene, etc. It is further developed to include the combustion of alternative fuels, like valerates and tri-esters.

Prof. Y. Bartosiewicz leads research activities about the ejection phenomenon including supersonic ejectors, two-phase ejectors and liquid jet-pumps as passive devices to improve thermo-mechanical systems. This activity is well balanced between theoretical developments (0D, 1D models), numerical simulations (CFD, 1D), and experimental investigations (flow visualizations, thermodynamic performances) at the component scale (ejector) as well at the system scale (thermal cycles incorporating an ejector). In particular, this includes, the study of physical issues such as transonic mixing, two-phase choked flows including metastable effects, and thermodynamic performances at the system scale. The applications cover solar cooling, low-grade heat recovery, and heat pumps. This research is essentially achieved through industrial and international collaborations

Prof. Y. Bartosiewicz also performs research in nuclear thermalhydraulics. This activity is mainly focussed in the development of numerical tools to tackle very specific issues related to pressurized water reactors (PWR) and liquid metal reactors (GENIV). For classical reactors (PWR), this includes the development and assessment of the delayed equilibrium model (DEM) for the flashing of pressurized water (loss of coolant accident, LOCA), and the simulation of wavy stratified flow including droplet entrainment in case of a pressurized thermal shock (PST).

For liquid metal reactors, state of the art CFD models using direct (DNS) and hybrid large eddy simulations (LES) are developed in collaboration of Prof. G. Winckelmans to tackle the issue of convective heat transfer within the frame of a very low-Prandtl fluid. This research is essentially done in the frame of EU projects and/local partners such as SCK•CEN.

Finally the link between applied fluid mechanics and applied energy is achieved by the work of the Prof. M.V. Papalexandris. Indeed, the research activities of the group of Professor M.V. Papalexandris are in theoretical and computational fluid mechanics with emphasis on complex fluids, two-phase flows, and reacting flows.

Ongoing projects include research in i) flows of granular mixtures with applications to sediment transport, and storage & transport of granular materials used in industry and agriculture, ii) reacting flows in porous media with application to forest-fire spread and biomass combustion, iii) two-phase supersonic combustion with application to accidental explosions, solid fuels and scramjet engines, and iv) premixed turbulent flames, with applications to gas turbines and industrial burners. The research activities encompass the development of mathematical models based on advanced theories of continuum mechanics and non-equilibrium thermodynamics, the mathematical and numerical analysis of these models, as well as algorithm development and detailed simulations based on High Performance Computing techniques.
The group of Professor Papalexandris maintains collaborations with research groups of the Paul Scherrer Institute-PSI and the the Federal Institute of Technology in Lausanne-EPFL (Switzerland), the University of Stuttgart, the University of Notre Dame (USA), the Universities of Thessaloniki, Patras & Crete (Greece), the University of Trieste (Italy), as well as with a number of companies (Fugro Geoconsulting, IdroStudi, Stucki, etc).

Transversally, The TFL division works under contract for several private companies and provides engineering services in different fields such as numerical simulations in fluid mechanics and heat transfer, data acquisition, calibration of measurement devices, and complete realization of prototypes from the design to the commissioning. Besides a strongly experienced technical team, the TFL division owns state of the art simulation tools, experimental facilities and measurement devices including:

- High performance computing
- CFD codes: ANSYS CFD, OpenFoam, plus home made
- High speed camera
- Schlieren apparatus
- High speed stereo PIV system
- Laser Doppler velocimetry (LDV)
- Low speed wind-tunnel (open)
- Towing tank (13m long)
- Fluid characterization lab
- Coriolis flow meters, temperature/pressure measurements
- Mass spectrometer

- Industrial compressor (delivering 1200 Nm3/h at 40bar)
- 200kWth gasifier
- Drop tube furnace
- Several engines
- Cogeneration units
- Ejector air conditioning
- Combustion chambers
- Large scale supersonic ejector

These features provide good conditions for a well-balanced approach integrating both numerical simulations and experimental verification to achieve research and engineering projects.