turbulentSyntheticEddyInlet

[Hursanay]

This PR adds turbulentSyntheticEddyInlet, a synthetic-turbulence velocity inlet for LES/DES, together with a tutorial case.

The condition generates inflow using a divergence-free synthetic eddy method. A population of virtual eddies is convected across the patch, with size, shape and strength such that the resulting velocity field reproduces the specified Reynolds stress tensor and integral length scale. The synthetic-eddy velocity field is divergence-free by design, thereby avoiding spurious pressure drops.

--- Features ---

• Simple setup:
  -- Reynols stress tensor and integral length scale distribution are automatically computed. The boundary condition bundles DNS channel flow data for different Reynolds numbers, and the most appropriate set is automatically selected at runtime.
  -- Walls and cyclic neighbor patches are detected automatically from the mesh. Wall-distance and direction are used to locally select the right integral length and Reynolds stress tensor and rotate it appropriately. Ghost eddies are created automatically to respect cyclic patches.
  -- Minimal usage is simply:
  inlet {type turbulentSyntheticEddyInlet; massFlow 1;}
  and works for any geometry
• Advanced setup: Most features are overridable by users. For example, one can specify velocity, Reynolds stress tensor and integral length profiles freely, and settings like eddy density etc. can be freely tweaked.
• Massflow or velocity can be time-dependent, and Reynolds stress tensors are updated to account for changes.
• Optional inlet self-correction at initialisation through Monte-Carlo simulation to account for the finite size of eddies.
• Optional downstream self-correction mechanism to adjust turbulence strength at the inlet such that the downstream intensity is matched, accounting for decay that often occurs near the inlet.
• Swirl can be specified through a swirl number.
• See reference for more details.

--- Tutorial ---

tutorials/fluid/turbulentSwirlAnnulus showcases a simple setup with turbulent swirling flow. Runs in a few minutes on 4 processors.

--- References ---

Method, derivation and validation:

• Fyhn, E. H., & Fyhn, H. (2026) turbulentSyntheticEddyInlet: A self-correcting, divergence-free synthetic-eddy boundary condition for OpenFOAM. SoftwareX, 35, 102907. https:://doi.org/10.1016/j.softx.2026.102907

• See also https://github.com/Hursanay/turbulentSyntheticEddyInlet for more thorough documentation and tutorial cases

Applications:

• H. Fyhn, A. Gruber, H. T. Nygård, J. Dawson, and K.-J. Nogenmyr, "Numerical and Experimental Investigation of a Non-Premixed Flame of Partially Decomposed Ammonia at Atmospheric Pressure," Journal of Engineering for Gas Turbines and Power (accepted, 2026).

• H. Fyhn, O. H. H. Meyer, Q. Wang, N. Worth, J. Koomen, T. Dammers, and A. Gruber, "Numerical and Experimental Investigation of a Laboratory-Scale Hydrogen-Fired FlameSheet™ Burner Operated at Atmospheric Pressure With Full Optical Access," Journal of Engineering for Gas Turbines and Power (accepted, 2026).

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