Effects of passive control rings positioned in the shear layer and potential core of a turbulent round jet
Bibliographic record
Abstract
Experimental measurements were carried out to study the effect of flow modification near the jet exit on a turbulent round free jet. To achieve this, two different fine rings, with square cross-sections, were designed and placed very close to the jet exit (x/D = 0.03). The first ring was placed in the middle of the shear layer while the second ring covered a small region of the potential core. Flying and stationary hot wire measurements were carried out to study the near- and intermediate-field development of the jet. Three Reynolds numbers (based on the jet exit mean velocity and the nozzle diameter) were used: 10 000, 30 000, and 50 000. The results show a considerable reduction in the jet spread rate and turbulence intensity when the passive rings are employed. This is more obvious for the ring placed in the shear layer. The radial profiles of the mean and rms axial velocity and third and fourth moments of fluctuations at several axial positions are considered. The power density spectra reveal the suppression of the initial shear layer instability (shear layer mode), while the jet preferred instability (preferred mode) remains active as the shear layer is modified. In the case when potential core modifications are used, the suppression of the initial shear layer instability is still considerable although there is an evidence of another vortical structure behind the ring, which, it is speculated, is due to the vortex shedding behind the ring. In this case, too, the jet preferred instability remains active. Therefore, the current paper confirms the separation of these two modes. In addition, the current contribution provides a comprehensive study of the characteristics of different length scales in the development region of the jet (e.g., integral scale, Taylor microscale, and Kolmogorov scale) for both the modified and unmodified jets.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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 source (direct Gemma or distilled Codex), 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".