Numerical study on the reinitiation mechanism of detonation propagating through double slits in a planar channel

Abstract

In this study, numerical simulations were performed to investigate the reinitiation of diffracted detonation waves through a double-slit-plate. A planar detonation wave was set to propagate through a channel of a height of 50 mm filled with the stoichiometric mixture of hydrogen and oxygen at 20 kPa. Several slit-plates with different slit widths and slit spacing were considered to explore the effects of slit geometry on reinitiation and its underlying mechanisms. For this, two-dimensional multi-species reactive Navier–Stokes equations were solved using a finite volume solver. The results revealed that upon diffraction, the detonation waves become decoupled and subsequently exhibit one of three distinct phenomena depending on the specific slit geometry. These phenomena include reinitiation by shock–shock interaction (RSSI), reinitiation by shock-wall interaction (RSWI), and complete suppression. It was found that a residual transverse wave is crucial in generating a detonation kernel. In cases where this residual transverse wave is absent, the detonation kernel fails to develop. As a result, only complete suppression of the detonation wave was observed. The narrow slit widths effectively suppress residual transverse waves through the steep expansion that occurs as the detonation front passes through the slit. Moreover, larger slit spacing resulted in further expansion of the shock front before the collision, due to the increased time delay for the shock waves to intersect. As a result, it was found that a larger slit spacing is unfavorable for the formation of a detonation kernel. Yet, in this regard, it is important to note that the onset of RSSI was not guaranteed even with a detonation kernel. Rather, the onset of RSSI was highly dependent on the curvature of the main detonation trajectory. RSSI was inhibited in cases where the forward propagating detonation wave experienced significant expansion due to the large curvature of the main detonation wave trajectory. Smaller slit spacing was found to be particularly unfavorable for RSSI as they exhibit more divergent curves. Overall, this study illustrates that the reinitiation mechanisms of detonation show two different pathways in the transition to detonation from decoupled shock waves and reaction fronts upon diffraction propagating through double slit configurations, and enhances understanding of RSSI by providing insights into the complex interplay between slit geometry, detonation kernel formation, and curvature of detonation wave based on highly-resolved numerical simulations using detailed chemistry. The findings from this study have implications towards the design and optimization of systems involving detonation propagation and suppression.Novelty and significanceThis study focuses on the reinitiation mechanism of detonation propagating through double slits in a planar channel. Specifically, this numerical study aims to understand the critical behaviors that occur when the slit width and the cell width of the detonation are comparable, based on the previously reported experiment. Reinitiation by shock–shock interaction which had previously been limited in understanding was explained in detail and the effects of slit geometry were examined. It is worth noting that there is a lack of in-depth explanations in the literature regarding the double slit configuration with various dimensions of slit-plates. Moreover, this investigation deals with smaller scales of slit width compared to the well-known critical length scale of a planar channel which is about ten times of cell width. As a result, the findings of this study offer further insights for optimizing the design of detonation arrestors.