Experimental Investigation of Small Amplitude Self-Sustained Pitch-Heave Oscillations of a NACA0012 Airfoil at Transitional Reynolds Numbers
Bibliographic record
Abstract
An experimental investigation of a rigid but free-mounted NACA0012 airfoil in pitch-heave is conducted at transitional Reynolds numbers. In previous works, small amplitude self-sustained oscillations of the airfoil in pure pitch were experimentally observed for a specific range of chord-based Reynolds numbers of 5.5×10 4 - 1.25×10 5 . Subsequent analysis confirmed the significance of laminar boundary layer separation in this regime, which leads to negative aerodynamic damping at 0 o AOA. These oscillations have been labeled laminar separation flutter by contrast to stall flutter, the latter occurring at high angles of attack and with minimal Reynolds number dependency. In this phase of our research, we extend the experimental investigation from one to two degrees of freedom by enabling the heave motion of the airfoil. The aeroelastic dynamics is studied for a variety of structural stiffness coefficients in heave. Depending on initial conditions, two competing steady state LCOs, small and large, are observed. It is determined that the origin of the large amplitude LCOs is coalescence flutter whose exponentially growing amplitude is limited by flow separation at large AOAs. On the other hand, the small amplitude oscillations are the same laminar separation flutter type as the pitch only case. Indeed 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 1DOF pitch only case, nor is the range of Re numbers at which the LCOs 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 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 | 0.000 |
| 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) | 0.002 | 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.
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