Experimental and numerical shadowgraph in turbulent Rayleigh-Bénard convection with a rough boundary: investigation of plumes

Abstract : We show that, in the case of turbulent Rayleigh-Bénard convection, shadowgraph can be used to have quantitative results on the plumes statistics and their velocity. It will be shown that the velocity of advection of the plumes is different from average velocity field. For this purpose, we compare the experimental shadowgraph of a Rayleigh-Bénard cell with the synthetic shadowgraph obtained by calculating the integrated 2D Laplacian of the temperature field from a numerical simulation very similar to the experiment. We demonstrate the use of image processing tools to enhance the quality of the shadowgraph image, and obtain quantitative statistics for the thermal plumes, such as plume density, and plume velocity distribution. The distribution obtained from processing the synthetic shadowgraph images of the DNS are compared to the fluid velocity at mid-plane. In a similar fashion, the velocity distribution of thermal plumes obtained from processing the experimental shadowgraph images, is compared to PIV measurements in mid-plane. To better highlight the goodness in the counting of plumes, we use a turbulent Rayleigh-Bénard convection cell with a rough bottom surface, and a smooth top surface, both in the experiment and in the numerical simulation. The asymmetric cell configuration, allows to directly compare plume statistics in each half-cell, and investigate how plate roughness changes the statistics of the thermal plumes.
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https://hal.archives-ouvertes.fr/hal-02329929
Contributeur : Julien Salort <>
Soumis le : mercredi 23 octobre 2019 - 17:25:31
Dernière modification le : jeudi 2 janvier 2020 - 14:58:03

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  • HAL Id : hal-02329929, version 1

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Mebarek Belkadi, Laura Guislain, Anne Sergent, Berengere Podvin, Francesca Chillà, et al.. Experimental and numerical shadowgraph in turbulent Rayleigh-Bénard convection with a rough boundary: investigation of plumes. 2019. ⟨hal-02329929⟩

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