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P. Le Quéré
Fluid Dynamics Group
Transfer Dynamics Group
Energetics Group
The Mechanical and Chemical Engineering Department is made of three groups:
- a Fluid Dynamics Group, which covers the studies dealing with turbomachines and external flows about bodies, both incompressible and compressible,
- a Transfer Dynamics Group, which covers studies in which the fluid motion is responsible of heat or mass transfer, ranging from thermo-solutal convection to coupled heat and mass transfer in complex geometries,
- an Energetics Group which covers studies ranging from the measure of kinetics diffusion coefficients to the design and testing of refrigerators or heat pumps using adsorption and studies on thermoacoustics in dense fluids and ebullition heat transfer.
The last group is made of the union of the old adorption group and of the Laboratoire of Thermodynamics of Fluids, under the heading of Pr M.X. François and located in a nearby building, that has been incorporated at the beginning of 1995. We have also grown by recruiting two new permanent researchers. One is L. Tuckerman, known for her contribution in the studies of instabilities and related numerical techniques, who was hired as a CNRS researcher in September 1994. The other is E. Gadoin, who did her thesis on the dynamics of two-phase flows in pipes, was hired as an associate professor with University Paris VI at the same date.
The research themes of the Department cover Fluid Dynamics, Thermal Sciences and Chemical Engineering. This is a very broad research field and our topics of interest are more precisely focused on the following research themes:
- Inverse methods for the design of turbine blades
- Separated flows around wings and bodies
- Fluid flow and heat transfer in enclosures
- Rotating disc flows
- Measurement of coefficients of kinetics of diffusion
- Modelling of adsorption columns
- Thermoacoustics in dense fluids
The major achievements during the previous years in each theme are the following:
- numerical analysis and development of projection methods
- application of inverse methods to the design of propellers
- simulation of turbulent flows about airfoils with large eddy techniques
- instability of the 3D natural convection flow in a cubic box
- investigation of transition to unsteadiness in rotating disc flows
- development of a software for the diphasic cooling of car engines
- determination of kinetics diffusion coefficients by volume modulation
- new results on validity Darcy's law and its non-linear corrections
Generally speaking, the studies fall into two main categories: either studies with a strong emphasis on methodology, or studies which use operational tools to investigate configurations involving fluid flow or heat and mass transfer. The aim of the methodological studies is to improve our investigation tools, and this is true of experimental as well as of numerical studies, since it is clear that numeriscists, like experimentalists, constantly have to improve their tools, to perform experiments of good quality, either in the lab or in the computer memory.
Both the Fluid Dynamics Group and the Transfer Dynamics group share the same methodology, that is the numerical solution of the Navier-Stokes equations, the main difference being that the origin of the movement lies in body forces on one side, whereas it is mainly due to a pressure gradient in the other group. Over the past two years, the emphasis has been put on the simulation of weakly turbulent flows, either with direct simulations or with large eddy techniques. In particular direct simulations of fully chaotic natural convection in differentially heated cavities have been performed for very large values of Rayleigh number, and simulations of strongly separated flows around an airfoil with large eddy techniques. As said above, improvement of the numerical tools is an important part of these two groups activity, and we have made some progress in the understanding and numerical analysis of the projection methods and developed a new projection method (called diffusion projection) for spectral polynomial approximations. Also substantial progress was made in the velocity-vorticity formulation for the incompressible Navier-Stokes equations, which is mainly used to compute external flows about bodies, due to the ease of imposing boundary conditions at infinity. It is also noted that the numerical algorithms initially directed at simulation of turbulent compressible flows around wings or bodies, have been extended to the computation of transonic jets in dense fluids near their critical point. Since these studies are mainly numerical, collaborations are sought with experimentalists, and close relationships exist with several groups in France, in Poitiers for 3 different studies, in Grenoble, in Nantes, in Paris...
The activity in the Energetics group is more balanced between laboratory experiments and numerical modelizations and simulations. The determination of the kinetics diffusion coefficients of various couples adsorbent/adsorbed is one of the major research themes and to this aim a novel technique based on cyclic volume modulation was developed. It produces coefficients of improved accuracy by comparison with measures with classical step functions techniques. The simulation and improvement of processes (refrigerators and heat pumps) using adsorption technique is another major research theme: this requires materials with good adsorption capacity and good heat transfer properties while not suffering of too large pressure drops, and at the same time the conception of new or improved thermodynamic cycles. One new research theme is the study of thermoacoustics in dense fluids for refrigeration purposes. These experimental studies are backed up with numerical simulations and modelizations, both as a help to interpret the experimental measurements or for themselves in the modelling of the behaviour of adsorption columns. Stokes or weakly non linear flows in periodic boxes have also been investigated theoretically and numerically and new result on the validity of Darcy's law and its weakly non-linear corrections have been obtained.
Most of the studies which are done correspond to contracts, either with national agencies (DRET, ADEME, CNES,..) or with private companies (RENAULT, VALEO, ELF, SNEA,..). A net increase of the European contracts is noted in the adsorption group.
Researchers of the Department have many relationships with foreign researchers. Pr. O. Talu, from Cleveland State University, is with us for a one-year sabbatical, and works on the co-adsorption of polar molecules. Other researchers have come for short stays : Professor Ruuthven in the Adsorption group, Professor L. Quartapelle in the Fluid Dynamics group.
F. Meunier is on the editorial board of 3 archival journals