用可解释深度学习揭示湍流动能方程的物理机制,发现近壁区耗散主导结构组织。
Explainable deep learning reveals the physical mechanisms behind the turbulent kinetic energy equation
- 基于SHAP的可解释模型识别湍流动能预算项的关键结构
- 近壁区耗散结构主导生产与粘性扩散,形成层级组织;外层则消失
- 经典相干结构无法解释各区域动能机制,适合流体力学与机器学习交叉研究者
本文利用可解释深度学习(XDL)研究湍流动能输运的物理机制。基于SHapley Additive exPlanations(SHAP)的XDL模型,识别了摩擦雷诺数为$Re_τ=125$的湍流通道流中湍流动能预算项演化的高重要性结构。结果表明,重要结构主要位于近壁区,多与扫掠事件相关。在黏性层中,生产与粘性扩散相关的SHAP结构几乎完全包含于耗散相关结构内,揭示出近壁湍流清晰的层级组织。在外层,该层级结构瓦解,仅保留速度-压力梯度相关和湍流输运的SHAP结构,空间重合度约为60%。最后,我们证明经典研究的相干结构无法全面表征通道内各区域湍流动能预算项的机制。结果表明,耗散是近壁湍流的主要组织机制,将生产与粘性扩散约束于单一结构层级中,而该层级在外层破裂。
原文摘要 · Abstract (English)
In this work, we investigate the physical mechanisms governing turbulent kinetic energy transport using explainable deep learning (XDL). An XDL model based on SHapley Additive exPlanations (SHAP) is used to identify and percolate high-importance structures for the evolution of the turbulent kinetic energy budget terms of a turbulent channel flow at a friction Reynolds number of $Re_τ= 125$. The results show that the important structures are predominantly located in the near-wall region and are more frequently associated with sweep-type events. In the viscous layer, the SHAP structures relevant for production and viscous diffusion are almost entirely contained within those relevant for dissipation, revealing a clear hierarchical organization of near-wall turbulence. In the outer layer, this hierarchical organization breaks down and only velocity-pressure-gradient correlation and turbulent transport SHAP structures remain, with a moderate spatial coincidence of approximately $60\%$. Finally, we show that none of the coherent structures classically studied in turbulence are capable of representing the mechanisms behind the various terms of the turbulent kinetic energy budget throughout the channel. These results reveal dissipation as the dominant organizing mechanism of near-wall turbulence, constraining production and viscous diffusion within a single structural hierarchy that breaks down in the outer layer.
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