Sediment entrainment to the lee of roughness elements: Effects of vortical structures
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Bibliographic record
Abstract
This paper investigates the role of vortical structures shed by a roughness element, particularly the paired counterrotating vortices found in the element's wake, in the initiation of sand transport under conditions of both fluid and impact entrainment. Patterns of particle entrainment by fluid stress only were observed in wind tunnel studies employing narrow spanwise strips of sediment (277 μ m mean diameter), which minimized dislodgement by particles transported from upwind. Composite images of the erosional patterns clearly illustrate regions of the bed where shear stress is above, equal to, and below fluid threshold in the vicinity of the roughness elements. The results clearly show that elevated shear stress allows entrainment to occur in the vicinity of the horseshoe and paired counterrotating vortices at wind speeds otherwise insufficient for entrainment on a smooth bed. Impact entrainment was observed using the same methodology, with a supply of saltators introduced to the airstream through an upwind particle feed. The grain‐borne momentum of the saltation cloud greatly reduced the influence of the vortices on the rate of entrainment. However, the vortices were seen to influence the proportion of grains entering the different modes of transport (saltation, reptation, and traction). The obstruction of the saltator's trajectory by the roughness elements allowed sand tails to form to their lee under saltation, as compared to the clean air experiments in which the sand tails did not form.
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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 | 0.001 | 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 | 0.001 | 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 it