Chapman-Jouget point

Fast deflagration—the flame position is much closer to the precursor shock wave. Overdriven detonation—a transition to detonation that has just occurred and the detonation is significantly overdriven with the peak pressure, well in excess (2-3 times) of the value usually associated with a steady Chapman-Jouget (CJ) detonation. This peak pressure generated during the transition process is a particular point of concern in the industry. 

A consistent procedure was followed in measuring the records A median line was drawn through the oscillograph trace, starting at a point well beyond the wave front, and extending back up toward the peak to the point where it crossed the rise line. In this procedure, the contour of the expansion wave is extrapolated back to the shock front. The value obtained in this manner should be closely comparable to the Chapman-Jouget pressure. 

A plot of P vs. Up has the slope poDs and passes through the origin. If the Hugoniot curve for the detonation products of lead azide at the C-J point were known (the curve for unreacted RDX is known [40]), it would be possible to determine the strength of the shock wave generated in RDX by the detonation wave from lead azide. It is to be recalled that the Chapman-Jouget model as modified calls for a reaction zone at the end of which the reactants have been completely converted to products in equilibrium and travel at the local sonic velocity. The end of the reaction zone is often called the C-J plane, and the associated pressure and temperature called the C-J pressure and temperature. 

Cheetah is a thermochemical code that is used to predict detonation performance for solid and liquid explosives. Cheetah solves thermodynamic equations between product species to find chemical equilibrium for a given pressure and temperature. Chapman-Jouget (C-J) theory says that the detonation point is a state in thermodynamic and chemical equilibrium, so Cheetah can predict the properties of this state. From these properties and elementary detonation theory the detonation velocity and other performance indicators are computed. 

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