Multi-scale analyses of flow separation around rectangular prisms in uniform flow
Bibliographic record
Abstract
• Investigated turbulent flow around prisms with AR = 1, 2, and 3 using TR-PIV. • Identified dual-frequency vortex shedding unique to AR2 due to intermittent reattachment. • Used vorticity-based POD to resolve multi-scale coherent structures and KH instabilities. • AR2 showed largest spatial/temporal scales and broadest enstrophy distribution. • Demonstrated non-monotonic wake behavior with aspect ratio. Turbulent flows around infinitely spanned rectangular prisms in uniform flow with streamwise aspect ratios, AR = 1, 2, and 3 were studied using time-resolved particle image velocimetry (TR-PIV) at a Reynolds number of 16,200 based on free-stream velocity and prism height. These aspect ratios span regimes that transition from direct shear layer shedding in the wake (AR1) to intermittent reattachment (AR2) and mean reattachment on the prism surface (AR3). The mean flow topology, Reynolds shear stress, and turbulent transport were analyzed. Spatiotemporal characteristics were investigated using two-point correlation, integral time scales, reverse flow areas, and proper orthogonal decomposition (POD) of the vorticity field. The results reveal non-monotonic variations of statistical and structural characteristics with aspect ratio. The case of AR2 possesses the largest recirculation region as well as the largest spatial and temporal scales of coherent structures. The wake exhibits quasi-periodic fluctuations concentrated in a single frequency for AR1, and AR3 but dual frequencies for AR2. The POD of the vorticity effectively decomposed a wide range of scales. Depending on the aspect ratio, spectra of the POD coefficients revealed concentrated spectral energy at the dominant vortex shedding frequency, its harmonics and at Kelvin-Helmholtz instability frequencies associated with small-scale vortices near the leading edge.
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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 | 0.001 | 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".