Large eddy simulation of turbulent flow in a square annular duct
Bibliographic record
Abstract
The fully developed turbulent flow in a straight square annular duct is simulated using large eddy simulation (LES). The flow Reynolds number is 200 based on the mean friction velocity and half the hydraulic diameter of the annular duct. A grid refinement study is carried out using 130×66×66 (0.57 million) and 130×130×130 (2.2 million) control volumes, respectively. The mean flow field and the turbulent statistics are compared with existing experimental and numerical data for square duct flow. Acceptable agreement is obtained. A universal relation between the mean streamwise velocity and the distance away from a concave 90° corner along the corner bisector is derived by curve-fitting the results from both LES in a square annular duct and direct numerical simulation in a square duct. The results from the present investigation exhibit the distinctive secondary flow of Prandtl second kind, which consist of a chain of counter-rotating vortex pairs around both convex and concave 90° corners in the annular duct. Mechanisms responsible for the generation of the secondary flow are interrogated by analyzing the anisotropy of the Reynolds stress distributions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".