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Wall modeling for Large-Eddy Simulations of turbomachinery flows

ED MEGEP – [Subject to defense authorization]

The aviation industry’s ambitious environmental and operational goals necessitate continuous advancements in propulsion systems, focusing on efficiency, emissions, and noise reduction. Computational Fluid Dynamics (CFD) plays a pivotal role in achieving these objectives by simulating flows in components like compressors, turbines, combustion chambers, and exhaust systems. Among CFD techniques, Large Eddy Simulation (LES) stands out as a high-fidelity approach for capturing turbulent flow dynamics and loss mechanisms in turbomachinery. However, the significant computational cost of LES, especially for high Reynolds number flows in complex geometries, remains a significant barrier to widespread practical applications. Wall models offer a solution by modeling near-wall behavior rather than fully resolving it, thus reducing computational demands while preserving numerous advantages of LES.
The objective of this thesis is to tackle some of the challenges of wall modeling to ensure the physical relevance of wall models for turbomachinery and improve their integration within the LES framework. A Thin Boundary Layer Equations (TBLE) wall model, designed to account for pressure gradient effects, was implemented in the massively parallel AVBP solver. Additionally, a stochastic fluctuation model used to correct sub-grid scale (SGS) models near walls was studied and enhanced to address the log-layer mismatch arising from the coupling between wall models and the LES solver.
Key results presented in this thesis include the validation of the implemented models, both independently and together, on the turbulent channel flow and periodic hill academic test cases. The models were subsequently applied to turbomachinery cases, including a high pressure turbine blade casecade and a fan rotor/stator setup.

Jury

Xavier Gloerfelt	ENSAM	Rapporteur
Alexis Giauque	ECL	Rapporteur
Maria Vittoria Salveti	Universita di Pisa	Examinatrice
Ronan Vicquelin	CentraleSupelec	Examinateur
Koen Hillewaert	Université de Liège	Examinateur
Florent Duchaine	CERFACS	Directeur de thèse
Éric Lippinois	Safran Aicraft Engine	Membre invité
Thomas Grosnickel	Safran Helicopter Engines	Membre invité