Simulation of Detonation Initiation in Straight and Baffled Channels

Euler conservation equations, ideal gas state equations and simplified chemical kinetics models were used to simulate two-dimensional straight and baffled shock tubes. In a straight channel, detonation waves were initiated by a strong shock wave and allowed to travel down the channel to reach a CJ wave condition. It has been shown that a two-step reaction, kinetics model with an induction time delay, resulted in a physically plausible transient solution. The one-step kinetics model solution is only valid at the limit of a steady state CJ wave condition and should not be used for transient problems. The two-step kinetics model was then used to simulate a detonation initiation in a baffled shock tube. It was shown that the presence of multiple baffles in a channel could result in an initiation of detonation, in cases where the temperature jump across the traveling initial compression wave and the presence of a single baffle are not sufficient to initiate a detonation. Furthermore, it is shown that in the absence of any viscous mechanisms, shock reflection from the second baffle created a moving Mach stem between the baffles. The coalescence and focusing of pressure waves behind this Mach stem resulted in the creation of a hot spot leading to a detonation wave.