Laboratoire de Mécanique des Fluides et d'Acoustique - UMR 5509

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Accueil > Pages perso > Peter Spelt > Projets


Turbulence, évaporation, condensation.



Dispersed two-phase flows occur in many industrial applications and natural phenomena. In the past decade, significant progress has been achieved in this field, due both to a revolution in experimental techniques (PIV, PLIF, PTV. . .) and to the extraordinary development of numerical simulations. Interestingly, this domain has been tackled by different scientific communities, in Fluid Mechanics, Physics, Meteorology, or Geophysics, with different focuses and different methods. The case of inertial particles is an emblematic example, with the development of effcient Eulerian or Lagrangian models in Engineering, associated with deep insights in the dynamics of particle-turbulence interaction by physicists studying turbulence, which helped to improve current models. The participants to this project were involved in this global effort and mixing of scientific cultures in a previous ANR program DSPET, devoted to inertial particles. The case of dispersed flows involving mass transfer, due to evaporation, condensation, or dissolution or coalescence is even more intricate, due to the dependence in time of the size of the particulates (drops, bubbles, and particles), which precludes some convenient approximations such as point-particles and one-way coupling. Among the many fundamental difficulties of the problem, the present project objective is to focus on the interaction between turbulence and phase change in particulate flows. Although the specific features of flows with either drops, bubbles or particles make it unlikely that all situations can be described by a single general framework, we believe that common physical principles can be identified in all cases, and that much can be understood with the newly developed experimental and numerical tools. Since the problem is clearly multiscale, the project involves three steps corresponding (i) to a local study at the scale of the particles (Bubble, drop or solid particle), (ii) to the intermediate level (mesoscale) of a swarm of interacting inclusions, basically through turbulent induced collisions, (iii) to the macroscopic level of mean field equations used in applications. Although several aspects of the problem have been investigated, other important aspects, such as crossing trajectories effects and preferential concentration, or finite size e-ects on mass transfer and forces, have received little attention until recently. The goal of this proposal is to take advantage of recent advances in the investigation of this long-standing problem, by using the latest available techniques, and a strong coupling between experiments, simulations and modeling. The challenge is to determine both the evaporation/condensation rate along the trajectories, and the local characteristics of the continuous phase in the vicinity of the particle. Experimental techniques developed in the previous ANR program DSPET by the same group (high-speed PTV, high-speed holography, PIV+PLIF) appear to be well adapted for this purpose. Numerical methods accounting for severe evaporation conditions will also been developed. In a second methodological step, we shall consider situations involving many condensing/evaporating bubbles or drops. In such situations, phase changes can be greatly modified by two classes of mechanisms : collisions and coalescence processes, and collective effects. The first one involves essentially binary collisions between particulates, which are affected in a still incompletely understood way by turbulence.
The four teams involved in the project, at the LMFA, the Physics Laboratory at ENS Lyon, the LEGI and the OCA, gather some unique competences in advanced measuring techniques and theoretical and numerical modeling. They have a strong experience of common projects, and use to share experimental equipments and numerical codes.

Publications for this project wherein I was involved :

Thèse : Aurore Loisy (co-direction avec Aurore Naso)

A Loisy, A Naso and PDM Spelt 2017, Buoyancy-driven bubbly flows : ordered and free rise at small and intermediate volume fraction. Journal of Fluid Mechanics 816, 94-141. [@éditeur] [texte intégral (1er version)]

A Loisy, A Naso and PDM Spelt 2018, The effective diffusivity of ordered and freely evolving bubble suspensions. Journal of Fluid Mechanics 840, 215-237. [@éditeur]