Characteristic path analysis of confinement influence on steady two-dimensional detonation propagation

Abstract

Steady detonation in multi-dimensional flow is controlled by the chemical energy release that occurs in a subsonic elliptic flow region known as the detonation driving zone (DDZ). It is the region encompassing the detonation shock and sonic flow locus (in the frame of the detonation shock). A detonation that is strongly confined by material surrounding the explosive has the shock and sonic locus separated at the material interface. Information about the material boundary is traditionally believed to influence the DDZ structure via the subsonic flow on the boundary ahead of the sonic locus. A detonation that is weakly confined has the detonation shock and sonic locus intersecting at the material boundary. The sonic nature of the flow at the intersection point on the boundary is believed to isolate the DDZ structure from the material properties of the confinement. In this study, we examine the paths of characteristics propagating information about the confinement through the supersonic hyperbolic flow region that exists beyond the sonic locus, and determine whether these paths may impinge on the sonic locus and consequently influence the DDZ structure. Our configuration consists of a solid wall boundary deflected through a specified angle on detonation shock arrival, so that the streamline turning angle of the wall at the explosive edge is unambiguously defined. By varying the wall deflection angle from small through large values, we can systematically capture the evolution of the DDZ structure and the characteristic flow regions that influence its structure for strongly to weakly confined detonations. In all strong and weak confinement cases examined, we find that a subset of characteristics from the supersonic flow regions always impinge on the sonic locus. Limiting characteristics are identified that define the boundary between characteristics that impinge on the sonic surface and those that propagate information downstream of the sonic surface. In combination with an oblique-shock polar analysis, we show that the effects on the DDZ of characteristic impingement can be significant.

Detonation propagation for shock-driven, subsonic and supersonic confiner flow

“…A limiting HE C + characteristic, shown in figure 6(a), bounds the region of HE supersonic flow for which C + characteristics from the HE-SS boundary impinge on the sonic locus. This effect was recently identified by Chiquete & Short (2019), although they considered a specialised problem consisting only of the HE domain with an imposed HE-confiner interface shape. Here we show that the same behaviour occurs for multi-material flows where the confiner dynamics is accounted for.…”

“…Bdzil (1981), Stewart & Bdzil (1989), Vidal et al (1994), Gamezo & Oran (1997), Sharpe & Braithwaite (2005), Schoch, Nikiforakis & Lee (2013) and . Information about the confinement flow is transmitted to the subsonic DDZ region across the HE-confiner material interface, although Chiquete & Short (2019) have recently shown that propagation of information through the supersonic flow region in the HE, originating at the confinement boundary downstream of the DDZ, can also influence the DDZ structure. For higher density metal or alloy confiners, such as tantalum or stainless steel (SS), an oblique inert shock is transmitted into the confiner.…”

An analysis of three-dimensional patterns of experimental detonation cells

“…The lower flow velocity due to viscosity in a boundary layer acts as a mass sink that induces locally a specific mass larger than in the entire cross-section. The consequences are a diverging flow and, therefore, a curvature and a velocity deficit of the average front [64][65][66], that should increase with increasing thickness of the boundary layer. This description applies to cellular detonations if the cell widths are small enough compared to the transverse dimensions of the tubes so that a smooth average surface represents well the detonation front.…”

Effects of velocity shear layer on detonation propagation in a supersonic expanding combustor

“…Although there are certain differences in the detonation structures between twodimensional and three-dimensional simulations, 45 the two-dimensional simulation can also well represent the initiation and propagation process of the detonation wave. 46 The typical methods for shock-capturing introduce considerable numerical dissipation, which disturbs the physical diffusion part of the NS equations. To analyse the complex structure of flow field with the inclusion of various shock waves more accurately, the hybrid sixth-order weighted essentially non-oscillatory centered difference (WENO-CD) scheme 47,48 is utilised to solve the NS equations with chemical reaction.…”