Detonation initiation by reflection of a diffracting fast-flame off an obstacle
Bibliographic record
Abstract
The interaction of a diffracting fast-flame with a fence-type obstacle mounted on the channel floor was studied in a 12.7 cm by 7.6 cm rectangular channel. The fast-flame was generated by reflecting a Chapman-Jouguet detonation from a perforated plate. The fast-flame subsequently diffracted over a backward-facing step and reflected from an obstacle. The test section was designed such that two obstacle stand-off distances (SOD) (6.35 cm, 11.43 cm) and two obstacle heights (2.54 cm, 3.81 cm) were investigated. Test mixtures of 2 H 2 + O 2 and C 2 H 4 + 3 O 2 + 3 N 2 were studied, and the mixture reactivity was varied via the initial pressure in the range of 14 – 24 kPa. Side-view schlieren photography, chemiluminescence visualization, and soot-coated foils were utilized to investigate the interaction. For all channel configurations, detonation initiation directly due to shock reflection at the obstacle face (strong ignition) and shock-flame interaction-driven detonation initiation were observed. Shock focusing at the internal corner between the obstacle face and channel floor was responsible for generating strong ignition for the shorter 6.35 cm obstacle SOD. Strong initiation for the 11.43 cm obstacle SOD occurred following the normal reflection of a Mach stem off the obstacle face. If the Mach stem was shorter than the height of the obstacle at the time of collision, the reflection of the diffracting incident shock at the top external corner of the obstacle generated a transverse shock that propagated down the face of the obstacle which promoted strong detonation initiation. This effect is not factored in the existing critical strong detonation initiation criterion obtained for normal shock reflection off an obstacle.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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 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".