Quantitative Investigation of Coherent Structures in a Free Jet Using PIV and POD
Bibliographic record
Abstract
This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9 mm) into a stationary body of water. The jet exit velocity was 2.5 m/s and the exit Reynolds number was 22,500. Particle image velocimetry (PIV) measurements were made at the jet exit and in the far field of the jet. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis on the fluctuating velocity fields. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. Then, the identified vortex characteristics were analysed by performing a statistical study of their distributions. The results clearly reveal that the jet contains a substantial number of eddies of both rotation directions. Moreover, the number of vortices decreases in the axial direction while their size increases. The mean circulation magnitude is preserved in the axial direction. The results indicate that larger vortices have a higher value of circulation while smaller values of circulation are associated with smaller eddies.
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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".