Modélisation numérique de la couche limite atmosphérique en stratification thermique

National audienc

Modélisation physique de la dispersion atmosphérique à l'échelle d'un paysage hétérogène

National audienc

Un modèle numérique d'écoulement et de dispersion de particules à l'échelle d'un paysage hétérogène

National audienc

A fine-scale k-E model for atmospheric flow over heterogeneous landscapes

International audienc

Tracking Fronts in One and Two-phase Incompressible Flows Using an Adaptive Mesh Refinement Approach

International audienceNumerical computation is an essential tool for describing multi-phase and multi-scale flows accurately. One possibility consists in using very fine monogrids to obtain accurate solutions. However, this approach is very costly in time and memory size. As an alternative, an Adaptive Mesh Refinement method (AMR) has been developed in order to follow either interfaces in two-phase flows or concentration of a pollutant in one-phase flows. This method has also been optimized to reduce time and memory costs. Several 2D cases have been studied to validate and show the efficiency of the method

Direct numerical simulation of a freely decaying turbulent interfacial flow

International audienceWhereas Large Eddy Simulation (LES) of single-phase flows is already widely used in the CFD world, even for industrial applications, LES of two-phase interfacial flows, i.e. two-phase flows where an interface separates liquid and gas phases, still remains a challenging task. The main issue is the development of subgrid scale models well suited for two-phase interfacial flows. The aim of this work is to generate a detailed data base from direct numerical simulation (DNS) of two-phase interfacial flows in order to clearly understand interactions between small turbulent scales and the interface separating the two phases. This work is a first contribution in the study of the interface/turbulence interaction in the configuration where the interface is widely deformed and where both phases are resolved by DNS. To do this, the interaction between an initially plane interface and a freely decaying homogeneous isotropic turbulence (HIT) is studied. The densities and viscosities are the same for both phases in order to focus on the effect of the surface tension coefficient. Comparisons with existing theories built on wall-bounded or free-surface turbulence are carried out. To understand energy transfers between the interfacial energy and the turbulent one, PDFs of the droplet sizes distribution are calculated. An energy budget is carried out and turbulent statistics are performed including the distance to the interface as a parameter. A spectral analysis is achieved to highlight the energy transfer between turbulent scales of different sizes. The originality of this work is the study of the interface/turbulence interactions in the case of a widely deformed interface evolving in a turbulent flow

Contributions to heat and mass transfer between a plasma jet and droplets in suspension plasma spraying

International audienceKeywords: suspension plasma spraying droplet computational fluid dynamics heat and mass transfer In suspension plasma spraying, nano-sized particles are injected via a liquid or a solvent into a plasma jet. Due to shear by the plasma jet, the liquid is fragmented into small droplets flying into the gas flow. The present work has focused on a single droplet evaporating into the plasma environment, and considers, on the one hand, the physical analysis of the phenomena and, on the other hand, the characterization of the solvent's thermal and motion characteristics of evaporation by means of direct numerical simulation of a multiphase flow. Specific parameters such as the evaporation time of the droplet have been estimated. In addition, a validation study has been proposed by comparing numerical simulation and physical analysis. The direct numerical simulation of multiphase flow was based on a compressible 1-fluid model, modified for handling phase change. The employed numerical methods included the volume of fluid (VOF) approach for interface tracking and finite volumes on structured grids

Temperature mapping in a two-phase water-steam horizontal flow

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