Low-Frequency Dynamics of Flow over a Backward-Facing Step
Bibliographic record
Abstract
The low-frequency dynamics of turbulent flow downstream of a backward-facing step are examined by low-pass filtering the velocity fields from a long run-time large-eddy simulation. The low-frequency behaviors were found to set the location of streamwise reattachment. Examination of the instantaneous three-component velocity fields showed regions of flow where the streamwise velocity was momentarily driven all the way back to the step face. After the flow reaches the step, it is then directed along the step face in the spanwise direction, resulting in large regions of wall-normal vorticity . These large regions of vorticity are opposed by smaller regions of counter-rotating flow offset in the spanwise direction and were responsible for the spanwise variation of the reattattachment. The low-pass filtered streamwise velocity fields just above the lower wall showed significant spanwise oscillations with a mean wavelength of the streamwise low-pass filtered reattachment position of , consistent with previous studies at different Reynolds and Mach numbers. As the step geometry is homogeneous in the spanwise direction, this shows that this behavior is not the result of wall or edge effects, which is a conclusion that cannot easily be drawn from experimental studies with limited step-height-to-width ratios.
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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) | 0.000 | 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) | 0.000 | 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".