Marie Drouin's scientific contributions

This work aims to model turbulent flows in media laden with solid structures according to porous media approach. A complete set of macroscopic transport equations is derived by spatially averaging the Reynolds averaged governing equations. A two-scale analysis highlights energy transfers between macroscopic and sub-filter kinetic energies (dispersive and turbulent kinetic energies). Additional terms coming from the averaging procedure and representing solids/fluid interactions and turbulent contributions are modeled. Connections between turbulence modeling and dispersion modeling are presented. Other closure expressions are determined using physical considerations and spatial averaging of microscopic computations. A special care is given to the calibration methodology for the phenomenological coefficients. Results of the present model are successfully compared to volume-averaged reference results coming from fine scale computations and show significant improvements with respect to previous macroscopic models.

In a former paper, Drouin et al. [IJMF, 2010] proposed a model for dispersion phenomena in heated channels that works for both laminar and turbulent regimes. This model, derived according to the double averaging procedure, leads to satisfactory predictions of mean temperature. In order to derive dispersion coefficients, the so called ‘‘closure problem’’ was solved, which gave us access to the temperature deviation at sub filter scale. We now propose to capitalize on this useful information in order to connect dispersion modeling to wall temperature prediction. As a first step, we use the temperature deviation modeling in order to connect wall to mean temperatures within the asymptotic limit of well established pipe flows. Since temperature in wall vicinity is mostly controlled by boundary conditions, it might evolve according to different time and length scales than averaged temperature. Hence, this asymptotic limit provides poor prediction of wall temperature when flow conditions encounter fast transients and stiff heat flux gradients. To overcome this limitation we derive a transport equation for temperature deviation between the wall and the mean flow. The resulting two-temperature model is then compared with fine scale simulations used as reference results. Wall temperature predictions are found to be in good agreement for various Prandtl and Reynolds numbers, from laminar to fully turbulent regimes and improvement with respect to classical models is noticeable.

In this paper, turbulent flows in media laden with solid structures are considered. A complete set of macroscopic transport equations is derived by spatially averaging the Reynolds averaged governing equations. A two-scale analysis highlights energy transfers between macroscopic and sub-filter mean kinetic energies and turbulent kinetic energy. Additional terms representing solids / fluid interactions and turbulent contributions are modeled. Closure expressions are determined using physical considerations and spatial averaging of microscopic computations. Results of the present model are successfully compared to volume-averaged reference results coming from fine scale computations. Furthermore, this model is able to provide accurate boundary conditions for clear flow turbulent simulations.

In this paper, laminar and turbulent flows in channels are considered. The primary interest for industrial purpose is a macroscale description of mean flow quantities derived from the microscopic details of the flow in each subchannel. A double averaging procedure [16] and [17] has been used to derive balance equations for mean flow variables within laminar and turbulent regimes. This up-scaling procedure results in additional contributions, amongst which dispersion predominates. Thermal dispersion might be seen as the sum of a first contribution, hereafter denoted “passive”, due to velocity heterogeneities, and a second one, called “active”, due to wall heat transfer. The aim of the present work is to propose practical models for thermal dispersion that account for laminar and turbulent regimes. Embedded in CFD code, they are validated against RANS simulations. Our results illustrate the importance of thermal dispersion for heated flows in the presence of nonuniform wall heat flux or temperature jumps.