Evaluation of Turbulent Kinetic Energy Flux in a Bluff Body Stabilized Flame Subjected to a Mean Background Pressure Gradient

We study a bluff body stabilized premixed flame in a confined channel configuration featuring an augmented background pressure gradient to assess the mean directionality of the turbulent energy flux. In many non-reacting flows, turbulent kinetic energy flux occurs in a net down-scale direction (i.e., forward scatter), transferring energy from large scales of motion to progressively smaller scales. However, energy injection at small scales in reacting flows can lead to net up-scale transfer, known as backscatter, which can pose challenges for traditional models used in Large Eddy Simulations (LES). Here, we perform an a priori analysis on DNS data obtained from simulations of a bluff body stabilized premixed flame located within a nozzle-shaped channel using PeleLMeX, a low-Mach number reacting flow code based on the AMReX library. We find that the mean energy flux is in the net-upscale direction at some locations within the flame (varying as a function of the flame progress variable), indicating that backscatter is a key physical phenomenon to consider when modeling these types of reacting flow configurations.