Supervised learning & Data-driven methods
The proliferation of high-resolution datasets in turbulence due to advances in computing and algorithms over the past decade allows us to use data science as a viable tool to study turbulence. Machine learning-driven models have already attained spectacular success in fields such as language translation, speech and face recognition, bioinformatics, and advertising.
One of our research topics is to adapt these tools and apply them to persistent problems in turbulence research such as turbulence modeling and drag reduction.
H. J. Bae & A. Lozano-Durán, "Numerical and modeling error assessment of large-eddy simulation using direct-numerical-simulation-aided large-eddy simulation," submitted, 2023.
A. Lozano-Durán & H. J. Bae, "Machine-learning building-block-flow wall model for large-eddy simulation," Journal of Fluid Mechanics 963, A35, 2023.
H. J. Bae & A. Lozano-Durán, "DNS-aided explicitly filtered LES of channel flow," Annual Research Briefs, Center for Turbulence Research, Stanford University, 197-207, 2018.
Reinforcement learning
Reinforcement learning identifies optimal strategies for agents that perform actions, contingent on their information about the environment, and measure their performance via scalar reward functions. In this semi-supervised learning framework with foundations in dynamic programming, training is not performed on a database of reference data but is performed by integrating in time the model and its consequences to the flow field.
Applications for reinforcement learning in turbulence are diverse, such as turbulence modeling and flow control. Our goal is to utilize reinforcement learning in various applications involving turbulent flows.
D. Zhou, M. P. Whitmore, K. P. Griffin & H. J. Bae "Large-eddy simulation of flow over Boeing Gaussian bump using multi-agent reinforcement learning wall model," AIAA Aviation, 2023.
A. Vadrot, X. I. A. Yang, H. J. Bae & M. Abkar, "Log-law recovery through reinforcement-learning wall model for large-eddy simulations," Physics of Fluids 35, 055122, 2023
H. J. Bae & P. Koumoutsakos, "Scientific multi-agent reinforcement learning for wall-models of turbulent flows," Nature Communications 13, 1443, 2022 (selected Editors' highlights).