Further comments on weak detonations

A very convincing argument against the existence of weak detonations utilizes the results on detonation structure presented in Section 6.1.2.3. A ZND structure is not possible for weak detonations, and chemical reaction rates generally are not high enough to produce a direct transition to the end state. 

Weak detonations are believed to represent the condensation shocks observed in supersonic wind tunnels [12], [51]. Supercooled water vapor in a supersonic stream has been observed to condense rapidly through a narrow wave. The amount of liquid formed is so small that the equations for purely gaseous waves are expected to apply approximately. Since a normal shock wave would raise the temperature above the saturation point (thus ruling out the ZND structure, for example), and the flow is observed to be supersonic downstream from the condensation wave, it appears reasonable to assume that condensation shocks are weak detonations. This hypothesis may be supported by the fact that unlike chemical reaction rates, the rate of condensation increases as the temperature decreases. Proposals that weak detonations also represent various processes occurring in geological transformations have been presented [52]. 

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