Divergent Flow Effects in Gaseous Detonations

Gas detonations have become increasingly relevant due to the development of rotating detonation engines (RDEs), in which a steady detonation propagates around a thin annulus constantly fueled from an inflow at the bottom. In the shock-attached frame, the detonation front attaches to the bottom of the annulus perpendicular to the inflow. Depending on the fuel and RDE dimensions, at some standoff distance from the inflow, the detonation front transitions to a shear layer between the reacting flow and unburned (previously burned) mixture, which effectively acts as an outer boundary for the reacting flow. The standoff distance and angle of this shear layer directly affect the divergence experienced within the reacting flow. Here, we examine these effects directly via a series of hydrogen-air detonations in a 2D planar configuration. A shock-attached frame is imposed onto the flow, and the shear layer is represented as a streamline boundary. This configuration allows us to directly control the standoff distance of the shear layer as well as the flow divergence introduced via the shear angle. A series of studies are performed at varied standoff distances and shear angles to examine how these properties affect detonation propagation and heat release in RDE-like configurations.