Bibliographic record
Abstract
Starting jets emanating from a straight nozzle and orifices of different orifice-to-tube diameter ratios are investigated using time-resolved particle image velocimetry. The invariants of the motion, namely, the circulation, the hydrodynamic impulse, and the kinetic energy, are measured and compared to the classic slug-flow model, and this for both fixed exhaust speed and fixed diameter-based Reynolds numbers. An extension to the slug-flow model is proposed to account for the contraction the fluid is experiencing when being pushed out through orifice geometries. The contraction coefficients obtained for two-dimensional jets formed through a slit in a channel are applied to the axisymmetric problem. This modified slug-flow model is shown to better predict the invariants of the motion with discrepancies of the order of 10% compared to underpredictions of 130%, 50%, and 120% for the circulation, the hydrodynamic impulse, and the kinetic energy, respectively, using the classic slug-flow model. Moreover, for a fixed target exhaust speed, the model suggests the existence of a maximum in the production of impulse and energy at an orifice-to-tube diameter ratio of about 0.9, which was also observed experimentally for the kinetic energy. Practically speaking, this suggests that the most efficient way of producing a starting jet is using an orifice plate of ratio close to 1, but different from a straight nozzle. Finally, the overpressure correction of Krueger [“The significance of vortex ring formation and nozzle exit overpressure to pulsatile jet propulsion,” Ph.D. thesis (California Institute of Technology, 2001)] is applied and revisited to account for the orifice-to-tube diameter ratio. Overall, good agreement with the present experimental data is found.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".