Spatial features of Reynolds-stress carrying structures in turbulent boundary layers with pressure gradient
Bibliographic record
Abstract
We investigate the Reynolds-shear-stress carrying structures in the outer layer of non-equilibrium pressure-gradient turbulent boundary layers using four direct numerical simulation databases, two cases of non-equilibrium pressure-gradient boundary layers and two of homogeneous shear turbulence. We examine and compare the spatial organization and shapes of the Reynolds-shear-stress structures, specifically sweeps and ejections, across all cases. The analysis includes five streamwise locations in the boundary layers, varying in pressure-gradient sign, intensity, and upstream history. For the boundary layers, two types of three-dimensional velocity fields are considered: fully spatial fields and spatio-temporal fields using Taylor’s frozen turbulence hypothesis. Comparisons of the results indicate that the statistics of sweep and ejection shapes are sensitive to the choice of convection velocity in Taylor’s hypothesis. The sweep and ejection shapes are consistent across all flows when their sizes range from 1 to 10 Corrsin length scales, suggesting that mean shear plays a similar role in all cases, driving the formation of Reynolds-shear-stress carrying structures and contributing to turbulence production. Sweeps and ejections of different types form side-by-side pairs, while structures of the same type align in an upstream–downstream configuration. This behavior persists regardless of pressure gradient variations or upstream history, emphasizing the dominant influence of local mean shear.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".