Flow Structure of a Coaxial Circular Jet with Axisymmetric and Helical Instability Modes
Bibliographic record
Abstract
The flow structures in a coaxial jet with axisymmetric and helical instability modes for a comparatively low Reynolds number were investigated. The flow visualization and the measurements of velocities were carried out in an open water tank. In addition, three-dimensional numerical simulation of a coaxial jet was also performed using the commercial CFD software FLUENT 6.3. It was confirmed that the helical vortex was shed for the range of ratios of velocity of the inner to that of the outer jet from 0.5 to 1.0. Two characteristic flow regimes, i.e., axisymmetric and helical instability modes, were simulated in the flow field. For the coaxial jet with helical instability, the axial velocity along the centerline of the jet decreased more than that of the coaxial jet with axisymmetric instability. The axial velocity fluctuation at the centerline of the jet was small near the nozzle exit. However, the radial velocity fluctuation at that location increased. The convection velocity of vortices in the inner shear layer was larger than that for the outer shear layer. The convection velocity of vortices with the helical instability was slightly larger than that of the vortices with the axisymmetric instability. Consequently, the variation of velocity fluctuations and the convection velocity was associated with the arrangement of the vortex street in the shear layer.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".