Novel weak detonation initiation from normal shock reflection in square cross-section shock tubes
Bibliographic record
Abstract
Normal shock wave reflection driven detonation initiation was investigated in a 7.63-cm square cross-section shock tube using novel stereo visualization. High-speed schlieren video captured shock reflection and detonation onset through the sidewall of the shock tube, and simultaneously, self-luminous imaging through the end wall enabled the determination of the location of detonation onset in three-dimensional space. Tests were carried out with nitrogen- diluted stoichiometric ethylene-oxygen. Weak and strong detonation initiation modes were observed at the low and high end of the reflected shock temperature range tested, respectively. A novel reflected shock bifurcation driven weak detonation initiation mode was observed at intermediate temperatures where a flame, ignited at one, or multiple, reflecting wall corners, accelerated along the channel wall corner reaching the bifurcated reflected shock wave. The flame rapidly spread through the bifurcation stagnation bubble transitioning to detonation. The reflected shock temperature range that this new weak initiation mode was observed depends on the reflected shock pressure. For low reflected shock pressures, typical of historic detonation initiation shock reflection studies, this weak bifurcation mode was not observed. Nonreactive three-dimensional Navier-Stokes simulations showed that the reflected shock bifurcation generates flow conditions along the channel wall corners that can explain the observed flame propagation from the end wall to the stagnation bubble, and the subsequent rapid spreading in the stagnation bubble.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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 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".