The propagation and failure mechanism of gaseous detonations : experiments in porous-walled tubes
Bibliographic record
Abstract
In order to elucidate the propagation mechanism of detonations, the failure mechanism of detonations propagating in tubes with porous walls is investigated experimentally. Two distinct failure mechanisms were identified depending on the type of detonating mixture. Experiments in mixtures characterized by piecewise laminar reaction zone structures with weak three-dimensional effects revealed that the attenuation and failure is caused by the global mass divergence to the porous, permeable walls. The limits observed in these mixtures agreed very well with the theoretical limiting conditions for the existence of curved ZND detonations subjected to lateral expansions. Experiments were also conducted in a second class of mixtures, characterized by irregular cellular structures and turbulent reactions zones. When detonations in this class of mixtures are attenuated, transverse waves re-amplify from local instabilities in the reaction zone. This re-amplification permits the detonation wave to continue to propagate and overcome the effects of global mass divergence and transverse wave attenuation at the porous walls. Ultimately, when the rate of transverse wave re-generation is surpassed by the rate of transverse wave damping at the walls, the detonation can no longer be self-sustained and fails. The limits obtained in these irregular structure mixtures were found significantly wider than predicted by the ZND formulation, thus further confirming the important role of the three-dimensional turbulent structure in these detonations in providing a more efficient mechanism of gas ignition and propagation than detonations that exhibit a regular structure. The implications of the present study are that the ZND model is not valid in describing the reaction zone structure, the ignition mechanism and thus the propagation mechanism in these turbulent detonations. In these mixtures, the ignition mechanism is a combination of the classical mechanism of adiabatic shock compression leading to ignition as well as the intense turbulent mechanism usually attributed to deflagrations only.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".