Artificial neural network approach for turbulence models: A local framework

TL;DR

This paper introduces a local artificial neural network framework for turbulence modeling that accurately predicts RANS unclosed terms and outperforms traditional models in complex curved wall flows.

Contribution

The paper develops a local ANN-based turbulence model that effectively captures unclosed RANS terms and demonstrates superior performance over existing models in complex geometries.

Findings

LANN predicts RANS unclosed terms with correlation > 0.96.

LANN outperforms Spalart-Allmaras model in key flow predictions.

Model trained at low Reynolds number generalizes well to higher Reynolds numbers.

Abstract

A local artificial neural network (LANN) framework is developed for turbulence modeling. The Reynolds-averaged Navier-Stokes (RANS) unclosed terms are reconstructed by artificial neural network (ANN) based on the local coordinate system which is orthogonal to the curved walls. We verify the proposed model for the flows over periodic hills. The correlation coefficients of the RANS unclosed terms predicted by the LANN model can be made larger than 0.96 in an a priori analysis, and the relative error of the unclosed terms can be made smaller than 18%. In an a posteriori analysis, detailed comparisons are made on the results of RANS simulations using the LANN and Spalart-Allmaras (SA) models. It is shown that the LANN model performs better than the SA model in the prediction of the average velocity, wall-shear stress and average pressure, which gives the results that are essentially indistinguishable from the direct numerical simulation (DNS) data. The LANN model trained in low Reynolds number Re = 2800 can be directly applied in the cases of high Reynolds numbers Re = 5600, 10595, 19000, 37000 with accurate predictions. Furthermore, the LANN model is verified for flows over periodic hills with varying slopes. These results suggest that the LANN framework has a great potential to be applied to complex turbulent flows with curved walls.