Supersonic Nitrogen and Helium Jet Impingement on a Flat Stationary Surface
Bibliographic record
Abstract
Millimeter scale de Laval supersonic nozzles are used in cold spray additive manufacturing (CSAM) for spraying metal powder particles (5-100 µm) on a target surface with impact velocities of 300-1,500 m/s in their solid state. The kinetic impact energy allows particles to plastically deform and adhere to the target surface metallurgically and mechanically, which enables rapid repair of surfaces, deposition of coatings, and additive manufacturing of mechanical components. In CSAM processes, thermal history has significant influence on the final mechanical properties and the stress state of deposited materials with the largest source of thermal energy coming from the supersonic impinging jet with Reynolds numbers on the order 105-106. In this work, a parametric study was performed using CFD and an experimental apparatus for understanding the heat transfer phenomena between flat surfaces and millimeter scale supersonic jets impinging on the surfaces with Reynolds numbers reaching 2×106. An empirical relationship was then developed for estimating area averaged Nusselt numbers for Reynolds numbers ranging between 1×105 and 2×106 and for radii five to fifteen times that of the jet diameter. Within the bounds of the study, the nozzle to substrate standoff distance was observed to have little to no effect on the Nusselt number. Although developed for CSAM, the empirical correlations apply to other fields beyond CSAM.
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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) | 0.001 | 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".