Experimental Small-Amplitude Self-Sustained Pitch–Heave Oscillations at Transitional Reynolds Numbers
Bibliographic record
Abstract
An experimental investigation of a free-mounted rigid NACA0012 airfoil in pitch–heave is conducted at transitional Reynolds numbers. Previously, small-amplitude self-sustained oscillations in pure pitch were observed for a specific range of Reynolds numbers: . They were attributed to laminar boundary-layer separation, which leads to negative aerodynamic damping at a 0 deg angle of attack. In this phase of the research, the investigation is extended to 2 deg of freedom by enabling the heave motion. Depending on initial conditions, two competing stable limit-cycle oscillations, small and large, are observed. It is determined that the origin of the large-amplitude limit-cycle oscillations is coalescence flutter for which the exponentially growing amplitude is limited by flow separation at large angles of attack. On the other hand, the small-amplitude oscillations are the same laminar separation flutter type as the pitch-only case. For the most part, the heave motion plays no fundamental role in the dynamics, as the amplitude of the pitch oscillations is not drastically affected in comparison with the single-degree-of-freedom pitch-only case nor is the range of Reynolds numbers at which the limit-cycle oscillations are observed. Nonetheless, the heave motion contributes to the net transfer of energy from the flow to the structure, as the mean kinetic energy present in the oscillations is increased significantly compared to the pitch-only case.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".