This project addresses the turbulent combustion commonly encountered in gas-turbine engines, rocket engines, and industrial furnaces. Critical physical behavior occurs on sub-millimeter length scales, i.e., over length scales much smaller than the engine size. A study of the full range of design parameters to optimize performance requires large and computationally costly models. The project will uncover new relations between the large-scale combustor behavior and small-scale physics, and results will be applied to develop next generation combustion models. Detailed computations with artificial intelligence modeling will be leveraged to create highly efficient and accurate combustion models that can be used in designing new combustion devices. This project will guide sub-grid combustion modeling from direct numerical simulations of turbulent non-premixed combustion in a three-dimensional shear layer between an oxidizer stream and a fuel stream. The simulations will address a high-Reynolds-number shear layer with a planar mean flow. In the post-processing of results, statistical data will be collected concerning relative vector alignments and magnitudes of vorticity, normal strain rates, scalar gradients, and joint-probability density functions of these rates and gradients. Scaling rules for these magnitudes over the turbulent length-scale spectrum will be sought, to provide inputs for Reynolds-averaged Navier-Stokes computations and large-eddy simulations. The results will