Characterizing Fluctuations in Propagating Detonations

Joanna M Austin, Aerospace Engineering, UIUC

In detonation, the coupling between fluid dynamics and chemical energy release is critical. The reaction rate behind the shock front is extremely sensitive to temperature perturbations and, as a result, detonation waves in gases are always unstable.
A broad spectrum of behavior has been reported for which no comprehensive theory has been developed. The problem is extremely challenging due to the nonlinearity of the chemistry-fluid mechanics coupling and extraordinary range of length and time scales exhibited in these flows. Past work has shown that the strength of the leading shock front oscillates and secondary shock waves propagate transversely to the main front. In some highly unstable systems, intensely wrinkled reaction fronts have recently been observed. A key unresolved issue has emerged: How do the instabilities of the shock front at different scales influence the combustion mechanism?