Shear Layer Disturbance Growth rates in a Reacting Jet in Crossflow

Shear layer instabilities and rollup in the reacting jet in crossflow (RJICF) flow field are strongly influenced by the flame. In particular, prior experimental studies at atmospheric pressure show that the radial position of the flame with respect to the jet shear layer is an important bifurcation parameter where: 1) rapid shear layer roll up is observed when the flame is on the crossflow side of the shear layer (R1 configuration) and 2) completely suppressed when the flame is positioned in the jet side of the shear layer (R2 configuration) at atmospheric conditions. This difference in roll up behavior was hypothesized to be due to the significant difference in shear layer Reynolds number for the two configurations, as the shear layer lies directly in very hot gas in the R2 configuration. This work presents results using large eddy simulations of both the R1 and R2 configuration at elevated pressure while holding key kinematic and chemical properties constant. The idea of the elevated pressure simulations is to increase the Reynolds number for the R2 configuration to comparable values of the R1. It is observed that shear layer vortices quickly grow and rollup in the R2 at elevated pressures, supporting the Reynolds number hypothesis. Several candidate definitions of Reynolds number are provided to best describe this observed behavior.