Turbulent/non-turbulent interfaces in equilibrium and non-equilibrium regions in the absence of mean shear

M. Zecchetto, T. Watanabe, K. Nagata, C. B. da Silva  

Turbulent/non-turbulent interfaces in equilibrium and non-equilibrium regions in the absence of mean shear

International Journal of Heat and Fluid Flow, 103 109198 2023

This article may be found at https://doi.org/10.1016/j.ijheatfluidflow.2023.109198.

Accepted manuscript is available here. 
This version is free to view and download for private research and study only. 

Abstract

Direct numerical simulations (DNS) of turbulent fronts evolving into a non-turbulent flow region in the absence of mean shear are generated for both classical (equilibrium) and non-equilibrium turbulence in order to study the characteristics of the turbulent/non-turbulent interface (TNTI) that separates regions of turbulent from non-turbulent (or irrotational) flow. The effects of the non-equilibrium can be observed in a number of statistics computed in the turbulent core region of the turbulent evolving fronts, such as the Reynolds dependance of the normalised dissipation Cɛ, which exhibits a power law (for non-equilibrium turbulence) close to Cɛ~Reλ^(-n), where Reλ is the Taylor based Reynolds number and n≃1is a constant. However the non-equilibrium condition of the turbulent core region does not affect the main characteristics of the TNTI layer bounding this region, which is similar in equilibrium and non-equilibrium turbulence. In particular, the thickness of the TNTI layer is similar in both equilibrium and non-equilibrium turbulence.

日本語訳 (DeepL翻訳)

平均せん断が存在しない平衡領域および非平衡領域における乱流／非乱流界面

乱流領域と非乱流（または非回転）領域を分離する乱流／非乱流界面（TNTI）の特性を研究するために，平均せん断が存在しない状態で非乱流領域へと発展する乱流前線の直接数値シミュレーション（DNS）を，古典的（平衡）乱流と非平衡乱流の両方について作成した．非平衡の効果は、乱流コア領域で計算される多くの統計量、例えば、正規化散逸Cɛのレイノルズ依存性などで観察することができ、これはCɛ~Reλ^(-n)に近いべき乗則を示します（Reλはテイラー基準のレイノルズ数、n≃1は定数）。しかし、乱流コア領域の非平衡状態は、この領域を境界とするTNTI層の主な特性には影響を与えず、これは平衡乱流でも非平衡乱流でも同様である。特にTNTI層の厚さは、平衡乱流でも非平衡乱流でも同様である。

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