Merging of coherent structures in a separation bubble
Bibliographic record
Abstract
This work examines the spatio-temporal evolution and interaction of coherent structures in a laminar separation bubble (LSB) when left to develop naturally and excited acoustically. The investigation is carried out in a wind tunnel using a NACA 0018 airfoil model at a chord Reynolds number of 125000 and an angle of attack of 4°. Excitation is provided by an external acoustic source and planar, time-resolved Particle Image Velocimetry is used to characterize both the streamwise and spanwise flow development. It is shown that the separation bubble is receptive to acoustic disturbances applied at the first subharmonic of the most unstable disturbance frequency in the natural LSB, leading to the inception, growth, and decay of velocity fluctuations in the separated shear layer. These velocity disturbances are shown to manifest through periodic vortex merging − a process that otherwise occurs randomly in the natural flow. Assessment of the spanwise flow topology reveals that structures merge in a non-uniform manner along the span, with localized merging occurring away from where streamwise-oriented bulges develop in the two vortices involved in the pairing process.
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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".