Dynamics of Unsteady Inviscid and Viscous Detonations in Hydrogen-Air

The dynamics of one-dimensional, overdriven, hydrogen-air detonations predicted in the inviscid limit as well as with the inclusion of mass, momentum, and energy diffusion were investigated. A series of shock-fitted calculations was performed in which the overdrive was varied in the inviscid limit. The 0.97 MHz frequency of oscillation predicted for a f = 1.1 overdriven detonation agrees well with the value of1.04 MHz observed by Lehr in the equivalent shock-induced combustion experiment around a spherical projectile. As the initial overdrive is lowered, the long time behavior of the system becomes more complex, causing the amplitude of pulsations to increase and oscillations at multiple frequencies to appear. When the viscous analog of these detonations was simulated, it was found that viscous effects slightly alter the structure of a stable detonation and can significantly decrease the amplitude of pulsations in an unstable detonation.