Large Eddy Simulations of Turbulent Pipe Flows At Moderate-To-High Reynolds Numbers

TL;DR

This study uses wall-modeled Large Eddy Simulations to investigate turbulent pipe flows at high Reynolds numbers, assessing model accuracy and grid sensitivity, and demonstrating WALE's effectiveness in capturing flow physics efficiently.

Contribution

It evaluates the performance of various subgrid-scale models in high-Reynolds-number pipe flows and demonstrates WALE's accuracy and computational efficiency in such simulations.

Findings

WALE model outperforms OEEVM and SMG in accuracy.

Grid resolution criteria are critical for capturing small-scale turbulence.

LES with WALE accurately reproduces outer flow regions at high Re.

Abstract

Wall-bounded turbulence is relevant for many engineering and natural science applications, yet there are still aspects of its underlying physics that are not fully understood, particularly at high Reynolds numbers. In this study, we investigate fully-developed turbulent pipe flows at moderate-to-high friction velocity Reynolds numbers ($361 \leq Re_{\tau} \leq 2,000$), corresponding to bulk velocity-based Reynolds numbers of $11,700 \leq Re_{b} \leq 82,500$, using wall-modeled Large Eddy Simulations (LES) in OpenFOAM. A grid convergence study is performed for $Re_{\tau} = 361$, followed by an investigation of the accuracy of various subgrid-scale stress models for the same Reynolds number. Results show that the Wall-Adapting Local Eddy (WALE) model performs well compared to experiments and Direct Numerical Simulations (DNS), while One-Equation Eddy-Viscosity Model (OEEVM) and Smagorinsky (SMG) are too dissipative. LES utilizing WALE are then performed for four different Reynolds numbers with gradually refined grids, revealing excellent agreement with DNS data in the outer region. However, a significant deviation from DNS data is observed in the sub-viscous layer region, indicating the need for further mesh refinement in the wall-normal direction to accurately capture the smallest-scale motions' behavior. Additional mesh sensitivity analysis uncovered that, as the $Re_{\tau}$ value rises, it becomes crucial for a grid to adhere to the condition of $\Delta x^{+} \leq 20 - 25$ and $\Delta z^{+} \leq 10$ in order to precisely capture substantial large and small scale fluctuations. Overall, the WALE model enables accurate numerical simulations of high-Reynolds-number, wall-bounded flows at a fraction of the computational cost required for temporal and spatial resolution of the inner layer.