Stability of secondary vortex evolution in wake of oscillating foils
Bibliographic record
Abstract
The evolution of the secondary vortex arrangement around a foil, performing heaving and pitching motion, is numerically examined for a range of phase offsets (90 °≤ϕ≤ 270°) and reduced frequency (0.32 ≤Stc≤ 0.56), at a Reynolds number of 8000. The wake is dominated by two distinct systems of secondary hairpin-like structures. The first vortex system is associated with an elliptic instability, prompted by the paired primary and secondary leading edge vortices (LEV), which remains persistent within the entire range of Stc. However, the growth of the second system is more closely associated with undulations of the primary LEV at Stc≥ 0.40, which amplifies as it sheds downstream of the trailing edge. The characteristic presence of the first system is directly linked to the growth of the secondary LEV, formed due to the large-scale interactions under localized adverse pressure gradients. These features promote a streamwise flow compression in neighboring regions of the primary LEV. Subsequently, the stability of these wake arrangements is evaluated using dynamic mode decomposition technique, which identifies a neutrally stable state at the fundamental forcing frequency and its harmonics. However, an increase in the modulus of the first three modes, as Stc increases, coincides with stronger three-dimensionality in the wake. The fundamental mode characterizes the roller undulations, while subsequent modes reveal that the two systems of secondary hairpin-like structures are closely associated with the harmonics of forcing frequency.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".