Experimental transients of detonation re-initiation behind a single-hole obstacle: the effects of the tube cross-section shape
Résumé
We describe the scenarios of detonation re-initiation downstream of a single-hole obstacle in a straight tube depending on its cross-sectional shape, namely square or round. The tubes have the same crosssectional area of 16 cm 2 , and the holes have the same shape as that of the tubes, but different open area ratios. The reactive mixtures are 2 H 2 + O 2 + 2 Ar and 2 H 2 + O 2 . We used wall soot recordings, highspeed shadowgraphy or chemiluminescence imaging to obtain parietal and frontal views of the diffraction phenomena. We identify six behaviors, one subcritical, four critical, and one supercritical, depending on the initial pressure. The critical and supercritical behaviors are more easily obtained in the square tube than in the round tube, other parameters being equal. These transient effects of the cross-sectional shape can be observed where no effect would be observed for conditions of steady propagation. Inductively, this leads to discuss what dimensionality refers to experimentally for the global and local transients of detonation dynamics.
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