Transverse wave structure in detonations

Abstract

Transverse wave structure in detonations has been investigated using the smoked-foil technique in hydrogen-oxygen and acetylene-oxygen mixtures diluted with argon, helium or nitrogen. The experimental results may be interpreted to show that the nature of the transverse structure is not only dependent on the geometry of the detonation tube but is also dependent to some extent on the heat-capacity ratio of the explosive mixture. In particular, low-heat-capacity mixtures are shown to 1) couple more readily with the fundamental rectangular or planar modes of a rectangular tube, and 2) exhibit a more regular writing pattern during propagation. In addition, the delay to the spontaneous appearance of transverse structure during one-dimensional initiation has been measured and found to agree satisfactorily with a recent acoustic theory for the rate of growth of a transverse acoustic wave. Transverse wave spacing has been measured over a large range of dilutions and pressures in rectangular, planar, and circular tubes for both of these fuel systems, and these measured values have been compared to a very tentative finite amplitude theory based on a calculation of the shock-wave behavior during the refraction of opposing transverse interactions at their intersection. This calculation shows that the refraction behavior is particularly simple in some cases and, in addition, that the theoretical spacings bracket the experimental spacings for two different but quite reasonable assumptions concerning the extent of the reaction zone.