Processes in the region between a driving piston or contact surface and a strong shock wave (e.g. Mach number > 1.5) can be modelled theoretically as relatively small-perturbation events.
The combustion reaction is assumed to be of simple irreversible Arrhenius type; perturbations are then of the order of the dimensionless inverse activation energy (typically 1/25). Events behind the shock are then described by either an integral equation, which is solved by straightforward numerical iterative methods, or by a differential equation. The latter reveals the basic physics as a coupling between four limiting processes namely, explosion at constant pressure and at constant volume coupled with wave propagation at the isentropic and isothermal sound speeds.
Illustrative results demonstrate that induction activity within a fluid element takes place midway between constantvolume and constant-pressure limits, with appropriate influence on the time to ignition. Thermal expansion of fluid elements produces significant gas dynamical activity, whose influence is also evident in the strong dependence of induction time on weak modifications of contact surface behaviour.
Starting in 1946 as the College of Aeronautics, the Cranfield Institute of Technology was granted university status in 1969. In 1993 it changed its name to Cranfield University.