ROUGHNESS EFFECTS ON TURBULENT FLOW DOWNSTREAM OF A BACKWARD FACING STEP
Bibliographic record
Abstract
This study investigates the effects of surface roughness on turbulent shear flow downstream of a backward-facing step. Particle image velocimetry was used to conduct velocity measurements over two roughness elements and a reference smooth surface. In each test, the Reynolds number based on the step height and the centerline velocity was kept constant at 6750. The results show that roughness caused a marginal increase in the reattachment length. The distribution of the mean velocity, Reynolds stress, wall-normal transport of turbulent kinetic energy and spatial structures embodied in the two-point auto-correlation functions are independent of roughness in the recirculation region and immediately downstream of reattachment. Further downstream of reattachment, roughness reduced the streamwise mean velocity but increased the levels of the Reynolds stress, wall-normal transport of turbulent kinetic energy and the characteristic streamwise and wall-normal sizes of the spatial structures in the vicinity of the rough surface. Proper orthogonal decomposition is also used to reconstruct low-order representation of the flow field.
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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".