论文标题

通过深度学习预测动荡的通道的时间动态

Predicting the temporal dynamics of turbulent channels through deep learning

论文作者

Borrelli, Giuseppe, Guastoni, Luca, Eivazi, Hamidreza, Schlatter, Philipp, Vinuesa, Ricardo

论文摘要

在许多与湍流有关的应用中,复发性神经网络(RNN)的成功已得到证明,包括流量控制,优化,湍流特征再现以及湍流预测和建模。通过这项研究,我们旨在评估这些网络重现最小湍流流量的时间演变的能力。我们首先根据从流中采样的时间序列的傅立叶域(表示为FFT-POD)中获得基于模态分解的数据驱动模型。这种特殊的湍流情况使我们能够准确模拟靠近墙壁的最相关的相关结构。训练了长期 - 内存(LSTM)网络和基于库普曼的框架(KNF),以预测最小通道模式的时间动态。鉴于研究流量的复杂性,具有不同配置的测试突出了KNF方法的限制。从统计的角度来看,LSTM的长期预测显示出极好的一致性,相对于参考,最佳模型的错误低于2%。此外,通过使用Lyapunov指数和通过Poincaré地图的动态行为来分析混乱行为,强调了LSTM重现湍流时间动态的能力。探索了基于鉴定不同湍流结构的替代降低模型(ROM),并继续在预测最小通道的时间动力学方面表现出良好的潜力。

The success of recurrent neural networks (RNNs) has been demonstrated in many applications related to turbulence, including flow control, optimization, turbulent features reproduction as well as turbulence prediction and modeling. With this study we aim to assess the capability of these networks to reproduce the temporal evolution of a minimal turbulent channel flow. We first obtain a data-driven model based on a modal decomposition in the Fourier domain (which we denote as FFT-POD) of the time series sampled from the flow. This particular case of turbulent flow allows us to accurately simulate the most relevant coherent structures close to the wall. Long-short-term-memory (LSTM) networks and a Koopman-based framework (KNF) are trained to predict the temporal dynamics of the minimal-channel-flow modes. Tests with different configurations highlight the limits of the KNF method compared to the LSTM, given the complexity of the flow under study. Long-term prediction for LSTM show excellent agreement from the statistical point of view, with errors below 2% for the best models with respect to the reference. Furthermore, the analysis of the chaotic behaviour through the use of the Lyapunov exponents and of the dynamic behaviour through Poincaré maps emphasizes the ability of the LSTM to reproduce the temporal dynamics of turbulence. Alternative reduced-order models (ROMs), based on the identification of different turbulent structures, are explored and they continue to show a good potential in predicting the temporal dynamics of the minimal channel.

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