Collapse of a rectangular well in a quasi-two-dimensional granular bed
Bibliographic record
Abstract
We report on an experimental and numerical study of the collapse under gravity of a rectangular well in a quasi-two-dimensional granular bed. For comparison, we also perform experiments on the collapse of a single vertical step. Experiments are conducted in a vertical Hele-Shaw cell, which allows the flow to be recorded from the side using high-speed video. If the rectangular well is sufficiently narrow, the collapsing sidewalls collide at the center of the well and the dynamics of the collapse are dependant on the aspect ratio of the initial well. We follow the evolution of the free surface from the video images, and use particle image velocimetry to determine the subsurface velocity field. From these data, the potential and kinetic energy of the system are calculated. We observe two stages to the collapse flow: an initial gravity-dominated stage, during which the kinetic energy increases, and a later dissipation-dominated phase during which the kinetic energy decreases. We find that although both the width and depth of the depression that remains after the well has collapsed depend on the initial aspect ratio, the surface profiles are self-similar; that is, the shape of the final profile is independent of the aspect ratio of the initial well. We model the collapse of the well using a depth-averaged continuum model with basal friction and with a discrete element model. Both models give results which agree well with experiment. The discrete element model indicates that friction between the particles is the most important source of dissipation over the course of the collapse.
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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) | 0.001 | 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".