Super-resolution of turbulent velocity and scalar fields using different scalar distributions

Abstract

In recent years, sub-grid models for turbulent mixing have been developed by data-driven methods for large eddy simulation (LES). Super-resolution is a data-driven deconvolution technique in which deep convolutional neural networks are trained using direct numerical simulation (DNS) data to learn mappings between the input data from a low resolution domain to the super-resolved high resolution output domain. While the technique has been of a great success in a-priori tests, the assessment of its generalization capabilities is required for further a-posteriori applications. In this study we assess the generalization capability of a super-resolution generative adversarial network (GAN) in reconstructing scalars with different distributions. Forced turbulence mixing DNS data with a fixed Reynolds number but different bulk scalar distributions, are generated and used as training/testing datasets. The results show that the velocity vector field can be reconstructed well, but the model fails to super-resolve the scalars from out-of-sample distributions. Including two extreme mixture fraction distributions, namely double Pareto and semi-Gaussian, in the training dataset significantly improves the performance of the model, not only for those distributions, but also for previously unseen bimodal distributions.