Vortex Shedding and Spacing of a Rotationally Oscillating Cylinder
Bibliographic record
Abstract
Introduction T HE possibility of the suppression or elimination of vortex shedding is of considerable practical interest from the standpoint of wake modification and reduction of drag, as well as of flowinduced vibration. Various passive and active control schemes have been attempted to affect the vortex wake formation process. Recently, it has been shown that a considerable amount of control of the cylinder vortex wake can be achieved through rotational oscillation and that when the flow takes place in a fluid relative to a rotationally oscillating cylinder, a new series of flow phenomena could arise.1−4 Tenada1 studied the effects of rotational oscillation for Re(= du∞/ν, where ν is the fluid viscosity) ranging between 30 and 300, and indicated that, at very high oscillation frequency f0 and amplitude, the dead-fluid region behind a cylinder and the vortex-shedding process could be nearly eliminated. The amplitude is given by 1 = π θ f0d/2u∞ > 7–27, where θ is the peak-to-peak amplitude in degrees, d is the cylinder diameter, and u∞ is the freestream velocity. Recently, Filler et al.2 studied experimentally the frequency response of the shear layers separating from a circular cylinder subjected to small-amplitude oscillations, that is, 1 ≤ 0.03, for Re = 250–1200, and observed a coupling of the cylinder oscillations with both modes of vortex shedding, that is, shear-layer vortices and primary Karman vortex shedding. Filler et al. also reported that by rotationally oscillating the cylinder at or near the natural Karman frequency, the shear-layer instability was promoted and the Karman mode of vortex shedding was also affected. On the other hand, Tokumaru and Dimotakis3 have shown that large-amplitude ( 1 ≤ 16) and highfrequency ( f0/ fk = 1–20, where fk is the natural Karman shedding frequency) rotational oscillations, together with the spinning of the cylinder, can suppress the vortex shedding and produce significant reduction in the profile drag acting on the cylinder at Re = 1.5 × 104. The objective of this study was to investigate the variation of the lateral and longitudinal spacings of the shed vortices and the vortex formation with the cylinder oscillation at Re = 1.75 × 103 by the use of hydrogen-bubble and particle streakline flow visualization methods. Special attention was given to the study of the type of wake synchronization that might occur throughout an intermediate oscillation range ( f0/ fk < 4 and 1 ≤ 1.0), between those of Filler et al. and Tokumaru and Dimotakis.
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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".