2023-06-13 オークリッジ国立研究所(ORNL)
Simulations performed on Oak Ridge National Laboratory’s Summit supercomputer generated one of the most detailed portraits to date of how turbulence disperses heat through ocean water under realistic conditions. Credit: Miles Couchman
◆海洋の一部をモデル化し、リアルな条件下で乱流が熱を海水中に拡散させる様子を詳細にシミュレーションしました。これにより、汚染物質の拡散など他の物質にも応用可能な知見が得られました。これまでにない詳細さで乱流の特徴を明らかにし、長年の理論に矛盾する発見もありました。今後はより詳細な解析が可能となり、科学的な洞察がさらに進むことが期待されています。
＜関連情報＞
- https://www.ornl.gov/news/summit-study-fathoms-troubled-waters-ocean-turbulence
- https://www.tandfonline.com/doi/abs/10.1080/14685248.2023.2178654
減衰する成層乱流に対するプランドル数の影響について The effect of Prandtl number on decaying stratified turbulence
James J. Rileya ,Miles M. P. Couchman & Stephen M. de Bruyn Kops
Journal of Turbulence Published:15 Feb 2023
DOI:https://doi.org/10.1080/14685248.2023.2178654
Abstract
The effects of the variation in the Prandtl number on turbulence in a stably-stratified fluid is investigated by direct numerical simulation. The results of simulations are presented of the homogeneous decay of turbulence for a given initial Froude number and three different initial Reynolds numbers of increasing values. For each of these cases results for two different Prandtl numbers, 1 and 7, are shown. Various statistics are put forward, including kinetic and potential energy decay rates, kinetic and potential energy dissipation rates, buoyancy fluxes, energy spectra, and statistics conditioned on the local value of the vertical density gradient. It is found that the effect of increasing the Prandtl number is to increase the kinetic energy dissipation rate, while decreasing the potential energy dissipation rate. There is a notable transfer of potential to kinetic energy for the higher Prandtl number case. Finally there is evidence, based upon the analysis of vertical planes and statistics conditional on the local density gradient, that most irreversible mixing of both density and momentum occurs in regions of stronger static stability.
