Effects of a geometrical surface disturbance on flow past a circular cylinder: a large-scale spanwise wire
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Bibliographic record
Abstract
Flow control induced by a single wire that is attached on the outer surface and parallel to the span of a stationary circular cylinder is investigated experimentally. The Reynolds number has a value of 10 000 and the wire diameter is nearly two orders of magnitude smaller than the cylinder diameter, while being larger than the thickness of the unperturbed boundary layer forming around the cylinder. A technique of high-image-density particle image velocimetry is used to characterize mean and unsteady structures of the separating shear layer and the near wake. Only one of the shear layers is directly perturbed by the surface wire. This disturbance, however, has important global consequences over the entire near wake, provided that the wire is located within a certain range of angular positions with respect to the approach flow. Over this range, there are two angles that can be defined as critical on the basis of the streamwise extent of the near-wake structure. In a simplified sense, these critical angles are associated with significant extension and contraction of the near wake, relative to the wake in the absence of the effect of a surface disturbance. The critical angle of the wire that yields the most significant extension of the near wake is also found to lead to bistable oscillations of the separating shear layer at irregular time intervals, much longer than the time scale associated with the classical Kármán vortex shedding. The foregoing two critical states of extension and contraction of the near wake are, respectively, linked to attenuation or enhancement of the Kármán instability. Moreover, the onset of the shear-layer instability, Reynolds stress, Strouhal number and the transverse extent of shear-layer flapping are all shown to depend on the angular position of the wire within the defined range of angles.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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