Article (Scientific journals)
Wall Model Based on a Mixture Density Network to Predict the Wall Shear Stress Distribution for Turbulent Separated Flows
Boxho, Margaux; Toulorge, Thomas; Rasquin, Michel et al.
2025In Flow, Turbulence and Combustion, 115 (3), p. 1157 - 1180
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Keywords :
Conditional probability distribution; Machine learning; Separated flows; Turbulent boundary layer; Wall shear stress model; Wall-modeled large eddy simulation; Conditional probability distributions; Large-eddy simulations; Machine-learning; Stress models; Turbulent boundary layers; Wall shear stress; Wall-shear stress; Chemical Engineering (all); Physics and Astronomy (all); Physical and Theoretical Chemistry
Abstract :
[en] Most wall shear stress models assume the boundary layer to be fully turbulent, at equilibrium, and attached. Under these strong assumptions, that are often not verified in industrial applications, these models predict an averaged behavior. To address the instantaneous and non-equilibrium phenomenon of separation, the mixture density network (MDN), the neural network implementation of a Gaussian Mixture Model, initially deployed for uncertainty prediction, is employed as a wall shear stress model in the context of wall-modeled large eddy simulations (wmLES) of turbulent separated flows. The MDN is trained to estimate the conditional probability p(τw|x), knowing certain entries x, to better predict the instantaneous wall shear stress τw (which is then sampled from the distribution). In this work, an MDN is trained on a turbulent channel flow at the friction Reynolds number Reτ of 1000 and on the two-dimensional periodic hill at the bulk Reynolds number of 10,595. The latter test case is known to feature a massive separation from the hill crest. By construction, the model outputs the probability distribution of the two wall-parallel components of the wall shear stress, conditioned by the model inputs: the instantaneous velocity field, the instantaneous and mean pressure gradients, and the wall curvature. Generalizability is ensured by carefully non-dimensionalizing databases with the kinematic viscosity and wall-model height. The relevance of the MDN model is evaluated a posteriori by performing wmLES using the in-house high-order discontinuous Galerkin (DG) flow solver, named Argo-DG, on a turbulent channel flow at Reτ=2000 and on the same periodic hill flow. The data-driven WSS model significantly improves the prediction of the wall shear stress on both the upper and lower walls of the periodic hill compared to quasi-analytical WSS models.
Research Center/Unit :
A&M - Aérospatiale et Mécanique - ULiège
Disciplines :
Mechanical engineering
Aerospace & aeronautics engineering
Author, co-author :
Boxho, Margaux;  Cenaero, Charleroi, Belgium ; Department of Aerospace and Mechanics, ULiege, Liège, Belgium
Toulorge, Thomas;  Cenaero, Charleroi, Belgium
Rasquin, Michel;  Cenaero, Charleroi, Belgium
Winckelmans, Grégoire;  Institute of Mechanics, Materials and Civil Engineering, UCLouvain, Louvain-la-Neuve, Belgium
Dergham, Grégory;  Safran Tech, Châteaufort, France
Hillewaert, Koen  ;  Université de Liège - ULiège > Aérospatiale et Mécanique (A&M) ; Cenaero, Charleroi, Belgium
Language :
English
Title :
Wall Model Based on a Mixture Density Network to Predict the Wall Shear Stress Distribution for Turbulent Separated Flows
Publication date :
29 March 2025
Journal title :
Flow, Turbulence and Combustion
ISSN :
1386-6184
eISSN :
1573-1987
Publisher :
Springer Science and Business Media B.V.
Volume :
115
Issue :
3
Pages :
1157 - 1180
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
Safran - Safran Tech
Funding text :
Safran Tech and computational resources made available on the Tier-1 supercomputer of the F\u00E9d\u00E9ration Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the Grant Agreement No. 1117545.The funding of M. Boxho\u2019s Ph.D. project by Safran Tech is gratefully acknowledged. The present research benefited from computational resources made available on the Tier-1 supercomputer Zenobe of the F\u00E9d\u00E9ration Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the Grant Agreement No. 1117545, and from computational resources made available on Lucia, the new Tier-1 supercomputer of the Walloon Region, infrastructure funded by the Walloon Region under the Grant Agreement No. 1910247.
Available on ORBi :
since 23 October 2025

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