Log-law recovery through reinforcement-learning wall model for large eddy simulation

Aurelien Francois Vadrot, Xiang I. A. Yang, H. Jane Bae, Mahdi Abkar*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

This paper focuses on the use of reinforcement learning (RL) as a machine-learning (ML) modeling tool for near-wall turbulence. RL has demonstrated its effectiveness in solving high-dimensional problems, especially in domains such as games. Despite its potential, RL is still not widely used for turbulence modeling and is primarily used for flow control and optimization purposes. A new RL wall model (WM) called VYBA23 is developed in this work, which uses agents dispersed in the flow near the wall. The model is trained on a single Reynolds number ( R e τ = 10 4 ) and does not rely on high-fidelity data, as the backpropagation process is based on a reward rather than an output error. The states of the RLWM, which are the representation of the environment by the agents, are normalized to remove dependence on the Reynolds number. The model is tested and compared to another RLWM (BK22) and to an equilibrium wall model, in a half-channel flow at eleven different Reynolds numbers { R e τ ∈ [ 180 ; 10 10 ] }. The effects of varying agents' parameters, such as actions range, time step, and spacing, are also studied. The results are promising, showing little effect on the average flow field but some effect on wall-shear stress fluctuations and velocity fluctuations. This work offers positive prospects for developing RLWMs that can recover physical laws and for extending this type of ML models to more complex flows in the future.

Original languageEnglish
Article number055122
JournalPhysics of Fluids
Volume35
Issue5
Number of pages15
ISSN1070-6631
DOIs
Publication statusPublished - May 2023

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