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Grid-point and time-step requirements for direct numerical simulation and large-eddy simulation

★ ★ ★ ★ ☆

Paper Summary

Paperzilla title
Less Grid Points, More Science: Optimizing DNS & LES for Turbulent Boundary Layers

This study finds that the grid-point requirement for DNS of a spatially developing turbulent boundary layer is N ~ Re^2.05, less than previously thought. It also estimates time-step requirements for DNS and LES, suggesting that wall-modeled LES becomes increasingly more cost-efficient than wall-resolved LES and DNS as Reynolds number increases.

Explain Like I'm Five

Scientists found that when computers imagine how swirly air or water moves, they need fewer tiny boxes than they first thought. They also learned that for really big or fast swirls, one special way of imagining it works much faster for the computer.

Possible Conflicts of Interest

None identified

Identified Limitations

Reliance on Prior Work and Nested Grids
The estimates for DNS grid requirements are slightly different from those in Choi & Moin (2012) due to the use of nested grids in all three Cartesian directions. The estimates for WMLES are based on prior work and may not be completely accurate.
Limited Scope of Time-Step Analysis
The authors assume the use of semi-implicit codes for time-step estimation, which may not be universally applicable. The discussion of explicit treatment of viscous terms lacks detail.
Simplification of xo/Lx
The simplification of xo/Lx to a constant may not hold true for all flow scenarios, thus affecting the accuracy of time-step estimates.
Simplified Cost Analysis
The discussion of the computational cost is limited to back-of-the-envelope estimates and does not consider real-world performance on various hardware architectures.

Rating Explanation

This paper revisits prior estimates for grid-point requirements in DNS and LES of turbulent boundary layers, deriving more general estimates and providing a useful framework for optimization. The methodology is sound, but the reliance on certain assumptions and simplifications limits the broader applicability. Overall, a strong contribution to the field, warranting a rating of 4.

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Topic Hierarchy

Field: Engineering

File Information

Original Title: Grid-point and time-step requirements for direct numerical simulation and large-eddy simulation
Uploaded: July 14, 2025 at 06:54 AM
Privacy: Public