Turbulence in a Fluid Stratified by a High Prandtl-Number Scalar

Shinya Okino () and Hideshi Hanazaki ()
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Shinya Okino: Kyoto University, Department of Mechanical Engineering and Science, Graduate School of Engineering
Hideshi Hanazaki: Kyoto University, Department of Mechanical Engineering and Science, Graduate School of Engineering

A chapter in Sustained Simulation Performance 2017, 2017, pp 113-121 from Springer

Abstract: Abstract Turbulence in the fluid stratified by a high Prandtl-number (P r) scalar such as heat (P r = 7) or salinity (P r = 700) has been simulated by direct numerical simulations, using 40963 grid points. Computations have been performed using the 1024 nodes of NEC SX-ACE, which have enabled us to resolve the smallest scale of salinity fluctuations 700 ( ∼ 26 ) $$\sqrt{ 700}(\sim 26)$$ times smaller than the smallest eddy size. In our simulations, buoyancy initially affects only the large scale motions, and the k −1 spectrum predicted by Batchelor (J. Fluid Mech. 5:113–133, 1959) for a passive scalar could be observed in the spectrum of potential energy, i.e. the salinity fluctuations. However, as time proceeds, the buoyancy affects the smaller-scale motions, and the salinity fluctuations begin to show a unique spatially localised structure. At the same time, there appears a flat spectrum ( ∝ k 0) instead of the k −1 spectrum. The localised structure and the flat spectrum could be observed only for the salinity (P r = 700) and not for heat (P r = 7).

Keywords: High Prandtl Number; Smallest Eddy Size; Salinity Fluctuations; Passive Scalar; Direct Numerical Simulation (search for similar items in EconPapers)
Date: 2017
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DOI: 10.1007/978-3-319-66896-3_7

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