Unsupervised deep learning for super-resolution reconstruction of turbulence

TL;DR

This paper introduces an unsupervised deep learning model using cycle-consistent GANs for super-resolution of turbulent flows, enabling high-quality reconstruction without paired training data, thus broadening practical applications.

Contribution

The study presents the first unsupervised learning approach for turbulence super-resolution, capable of reconstructing high-resolution flow fields from unpaired data, unlike previous supervised methods.

Findings

Achieved comparable results to supervised models on paired data

Successfully reconstructed high-resolution flows from unpaired LES data

Demonstrated applicability to various turbulence datasets

Abstract

Recent attempts to use deep learning for super-resolution reconstruction of turbulent flows have used supervised learning, which requires paired data for training. This limitation hinders more practical applications of super-resolution reconstruction. Therefore, we present an unsupervised learning model that adopts a cycle-consistent generative adversarial network that can be trained with unpaired turbulence data for super-resolution reconstruction. Our model is validated using three examples: (i) recovering the original flow field from filtered data using direct numerical simulation (DNS) of homogeneous isotropic turbulence; (ii) reconstructing full-resolution fields using partially measured data from the DNS of turbulent channel flows; and (iii) generating a DNS-resolution flow field from large eddy simulation (LES) data for turbulent channel flows. In examples (i) and (ii), for which paired data are available for supervised learning, our unsupervised model demonstrates qualitatively and quantitatively similar performance as that of the best supervised-learning model. More importantly, in example (iii), where supervised learning is impossible, our model successfully reconstructs the high-resolution flow field of statistical DNS quality from the LES data. This demonstrates that unsupervised learning of turbulence data is indeed possible, opening a new door for the wide application of super-resolution reconstruction of turbulent fields.