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

Published online by Cambridge University Press:  15 May 2020

M. Belkadi Open the ORCID record for M. Belkadi [Opens in a new window] ,
L. Guislain Open the ORCID record for L. Guislain [Opens in a new window] ,
A. Sergent Open the ORCID record for A. Sergent [Opens in a new window] ,
B. Podvin Open the ORCID record for B. Podvin [Opens in a new window] ,
F. Chillà Open the ORCID record for F. Chillà [Opens in a new window]  and
J. Salort Open the ORCID record for J. Salort [Opens in a new window]
M. Belkadi
Affiliation:
LIMSI, CNRS, Université Paris-Saclay, Campus Universitaire, 91405Orsay, France Sorbonne Université, Faculté des Sciences et Ingénierie, UFR d’Ingénierie, 75005Paris, France Laboratory of Turbomachinery, Ecole Militaire Polytechnique, Bordj El Bahri, 16111, Algiers, Algeria
L. Guislain
Affiliation:
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, Lyon, France
A. Sergent
Affiliation:
LIMSI, CNRS, Université Paris-Saclay, Campus Universitaire, 91405Orsay, France Sorbonne Université, Faculté des Sciences et Ingénierie, UFR d’Ingénierie, 75005Paris, France
B. Podvin
Affiliation:
LIMSI, CNRS, Université Paris-Saclay, Campus Universitaire, 91405Orsay, France
F. Chillà
Affiliation:
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, Lyon, France
J. Salort*
Affiliation:
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, Lyon, France
*
†Email address for correspondence: [email protected]
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Abstract

We show that, in the case of turbulent Rayleigh–Bénard convection, shadowgraph can be used to gain quantitative results on the plume statistics and velocity. For this purpose, we compare the experimental shadowgraph of a Rayleigh–Bénard cell with the synthetic shadowgraph obtained by calculating the integrated two-dimensional Laplacian of the temperature field from a numerical simulation very similar to the experiment. We use 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. To highlight the efficiency of this new process of plume counting, we use, both in the experiment and in the numerical simulation, a turbulent Rayleigh–Bénard convection cell with a rough bottom surface and a smooth top surface, where the statistics of the plumes can be influenced (or not) by the roughness. In addition, the distribution of velocity obtained from processing the synthetic shadowgraph images of the direct numerical simulations (DNS) or the experimental shadowgraph images, are compared to the velocity fluid at mid-plane of the DNS or particle image velocimetry measurement in the experiment, respectively. It will be shown that the mean velocity profile measured using the advection of the plumes is different from the average Eulerian velocity profile.

JFM classification

Convection: Plumes/thermals
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 895 , 25 July 2020 , A7
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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