On the transition to 3D modes for channel flow past a square cylinder
Bibliographic record
Abstract
Abstract We consider the case of transient three‐dimensional, incompressible and isothermal channel flow of a newtonian fluid past a symmetrically confined obstacle of square cross section at zero incidence. The blockage ratio (ratio of cylinder diameter to channel width) is fixed at 1/4. Results from both Laser Doppler (LDV) experiments and direct simulations upto Reynolds numbers have been reported. Starting from the onset of instability ( ), close examination of the apparent region of influence that envelopes the cylinder reveals a clear vortex shedding signature which extends up to about three diameters upstream . While the fundamental vortex shedding frequency displays a fairly steady monotonic increase with Reynolds number, the Strouhal number (St) shows an inflexion point around . No signs of hysteresis were detected around this region. Furthermore, incommensurate harmonics observed for Reynolds numbers in the range suggest a quasi‐periodic transition to three‐dimensionality. This is shown to be followed by an intermediate periodic window starting around . Results from direct simulations performed using OpenFOAM (the Open Source CFD Toolbox) are used not only to enhance confidence in the accuracy of the reported LDV measurements, but also to help explain the observed phenomena through frequency power spectra and spanwise velocity correlations. Finally, it is concluded that only a parametric variation of transverse and spanwise blockage ratios can bring closure to the subject of bluff‐body wake transitions.
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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".