Direct numerical simulation of turbulent heat transfer in concentric annular pipe flows
Bibliographic record
Abstract
The effect of radius ratio on turbulent convective heat transfer within a concentric annular pipe has been studied using direct numerical simulation. Four radius ratios (Ri/Ro = 0.1–0.7) have been compared at a fixed Reynolds number, where Ri and Ro denote the radii of the inner and outer pipes, respectively. The statistical moments of the temperature field, budget balances of the temperature variance and turbulent heat fluxes, and turbulence structures that dominate the heat transfer process have been thoroughly studied in both physical and spectral spaces. It is observed that the radius ratio has a significant impact on the Nusselt numbers and skin friction coefficients of the inner and outer cylinder walls, and on the interaction of thermal boundary layers developed over these two curved walls. Owing to the curvature difference between the two cylinder surfaces, the thermal boundary layer developed over the outer cylinder wall is thicker than that over the inner cylinder wall. Also, turbulent heat transfer is more intense on the outer cylinder side than on the inner cylinder side. As the radius ratio decreases, the difference in turbulence statistics between the inner and outer cylinder sides becomes increasingly pronounced. It is also observed that both axial and azimuthal characteristic length scales of the most energetic turbulent thermal structures are larger on the inner cylinder side than on the outer cylinder side.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".