Concurrent Relationships between Physical and Fourier Space Representations of 3D Flow Structures for LES of Premixed Turbulent Combustion.*

In LES of premixed turbulent combustion, the subfilter scale (SFS) motions surrounding the flame have major dynamical impacts on the resolved scales (RS) of motion. Closure models are needed to capture dominant interscale couplings in turbulent combustion. As representative of dominant turbulent eddy-flame interactions, we inject arrays of vortex rings with specified length and velocity scales into a laminar premixed flame with chemical reaction and heat release. The interactions between the vortex rings and flame are analyzed in 3D Fourier space after removing non-physical Fourier content associated with the boundary discontinuity in periodic extensions in inhomogeneous directions. We show one-to-one correspondences between specific structural SFS and RS features in 3D physical space and Fourier space associated with the flame front, its deformations and space-filling motions local and nonlocal to the flame with corresponding 3D scale representation. We analyze a mix of spectrally nonlocal and local relationships between 3D coherent structure in physical space and 3D coherent structure in Fourier space with implications to interscale RS-SFS dynamics for LES of premixed turbulent combustion.