Fig. 1 : Champs instantanés de flux conductif à la paroi chaude (1000 °C) pour un nombre de Reynolds de 70000. En haut, les résultats d’une simulation numérique directe sont exposés ; en bas, ceux d’une simulation des grandes échelles de la turbulence.
These flows are highly complex because they are highly turbulent and asymmetrically heated. Characterized by very high temperatures reaching 1000°C, they are the seat of intense heat transfers and strong couplings between thermics and dynamics. The multi-scale approach developed has improved knowledge by filling gaps in the literature at each level, and provided models that will facilitate the industrial development of new tower power plants. The levels of study corresponding to detailed descriptions inform the more macroscopic levels of description.
At the microscopic scale, Direct Numerical Simulations (DNS) are carried out to approximate the understanding of interactions between turbulence and temperature [1] (unit cost: 4 million computing hours).
At the intermediate level, Large Scale Simulations (LSS) are carried out on less fine meshes, which drastically reduces computational costs (12,000 computational hours).
We aim to develop sub-mesh models that reproduce the effects of small-scale turbulence on resolved scales. Tests are carried out by comparing the results of each EMS with those of SND [2] (see figure). Thanks to these evaluations, we have identified a robust and accurate model. This was used to perform 70 EMSs to develop a correlation for estimating heat transfer in asymmetrically heated channels [3]. This constitutes a study at the macroscopic level, since the correlation can be used to carry out work at the scale of the solar receiver [4].