Multiple flow transitions in a box heated from the side in low-Prandtl-number fluids.
The determination of the flow transitions in a cavity heated from the side in low-Prandtl-number fluids has been a challenge for many years. Contrarily to the Rayleigh-Bénard situation, these transitions occur in already very intense convective flows, and the problem has been up to now mainly treated in two-dimensional situations. Thanks to a performing numerical method, the thresholds corresponding to the first flow transition in a three-dimensional (3D) parallelepipedic cavity have been determined for a wide range of aspect ratios and Prandtl number values. We obtain a kind of map of the transitions involved. Such a map of transitions is quite usual for Rayleigh-Bénard or Marangoni-Bénard situations, but completely new for 3D cavities heated from the side. The most striking result is the very frequent change of stability branches when the aspect ratios or Prandtl number are changed, which indicates different flow structures triggered at the thresholds, either steady or oscillatory, and breaking some of the symmetries of the problem.
Laboratoire de Mécanique des Fluides et d'Acoustique, CNRS/Université de Lyon, Ecole Centrale de Lyon/Université Lyon 1/INSA de Lyon, ECL, 36 avenue Guy de Collongue, 69134 Ecully Cedex, France.
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BenHadid