Wall-Modeled Large-Eddy Simulation of Turbulent Boundary Layers with Mean-Flow Three-Dimensionality

We examine the performance of wall-modeled large-eddy simulation (WMLES) to predict turbulent boundary layers (TBLs) with mean-flow three-dimensionality. The analysis is performed for an ordinary-differential-equation-based equilibrium wall model due to its widespread use and ease of implementation. Two test cases are considered for this purpose: a spatially developing TBL in a square duct with a 30 deg bend, and the flow behind a wall-mounted skewed bump with a three-dimensional separation bubble. In the duct simulation, WMLES is capable of predicting mean-velocity profiles and crossflow angles in the outer region of the flow to within 1-5% error using 10 points per boundary-layer thickness. The largest disagreement (20% error) is observed in the crossflow angles in the bend region, where three-dimensional effects are the most significant. In the skewed bump simulation, it is shown that the present equilibrium wall model with a grid resolution of about 40 points across the three-dimensional separation region predicts mean-velocity profiles and separation location to within 1-3% error. The bubble size and vortex structures in the bump wake are also correctly represented. It is demonstrated that WMLES is capable of achieving accurate results in the separated region and its vicinity, provided that the strong shear layer generated at the apex of the bump is well resolved.

Automated summary

The study shows that wall-modeled large-eddy simulation (WMLES) performs well in predicting turbulent boundary layers with three-dimensionality, accurately forecasting mean-velocity profiles and separation locations. However, in regions with significant three-dimensional effects, such as bends, prediction errors may increase.