In this report, the results of a theoretical and experimental investigation of the propagation of shocks and blast waves in a detonating gas are presented. In particular, cylindrical diverging detonations are studied in detail:​

In the theoretical phase of the investigation, analytical solut.ions have been obtained for two classes of problems:​ The first class involves a steady-state reaction front where self-similar solutions exists, and the second class of problems involve a non-steady reaction front where self-similar solutions are not possible.

For the class of self-similar flows, the propa.gation of Chapman-Jouguet detonations and piston driven reaction shocks are studied. The earlier works of Taylor and Zeldovich are extended and particular emphasis is placed on the physical interpretation of the results. For ston motion behind a diverging detonation wave, it was found that there exists a steady-stat.e secondary shock wave in the flow field between the piston and the detonation front. Experimental evidence of this secondary shock wave is obtained from the results of Behrens.

For the class of non-similar flows, the propagation of a blast wave in a detonating mixture has been analysed. Two non-similar analytical techniques have been developed for this problem;​ one based on Oshima" s quas simila.rity approximation and the other based on Porzel's assumption of a power law density profile. It was found that Oshima's method has a wider range of applicability than Porzel's method.

The results indicate that the initial stages of the blast propagation can be adequately described by Taylor's constant energy solution for a strong blast wave in a non-reacting gas. This is due to the fact that at small shoc~>. radii, the effect of the chemical energy release on the shock propagation is negligible as compared to the blast energy. The blast wave approaches a Chapman-Jouguet detonation wave at large shock radii when the chemical energy dominates the shock propagation.

In the experimental phase of the investigation, the phenomena associated with a finite reaction zone thidmess of the shock wave are studied. In particular, the initiation process and the mechanisms of propagation of cylindrical detonations are analysed. All the experiments are based on acetyleneoxygen mixtures at subatmospheric initial pressures.

For the direct initiation of cylindrical detonations, it was found that powerful igniters capable of releasing a large quantity of energy instantaneously are required. A critical ignition energy, below which a deflagration wave is formed, is obtained for every mixture composition at given initial conditions. This critical ignition energy was found to be dependent directly on the reaction zone thickness of the mixture.

The structure of diverging detonations is found to be similar to that of planar detonations. A non-planar front associated with localized "ignition headsu and transverse perturbations are observedo Turbulence is found to be an essential mechanism in the generation of additional "ignition heads" as the surface area of the detonation front increases.

From velocity measurements, the propagation velocities of cylindrical detonations are found to correspond to their Chapman-Jouguet values. Dependence of the detonation velocity on the thickness of the cylindrical bomb is not observed. The experimentally determined pressure profile behind a cylindrical detonation wave agrees fairly well with theory.

The mechanisms of deflagrative combustion behind a decaying blast wave are also described.