Adjoint-based optimization of large-scale reacting turbulent flow simulations

Despite recent progress in extreme-scale computing of fluid dynamic systems, its utility in design optimization remains challenging. The 'curse of dimensionality' generally precludes the use of high-fidelity simulations within a brute-force trial-and-error approach when seeking optimal design parameters. The adjoint of the perturbed and linearized flow equations presents a promising means of leveraging high-fidelity simulations for optimization. In this talk, we present a discrete adjoint-based method for measuring local sensitivity in direct numerical simulations (DNS) of turbulent reacting flows. We introduce a novel adaptive dissipation scheme compatible with a discrete adjoint formulation that preserves scalar boundedness while retaining high-order accuracy. A flamelet-progress variable approach is employed to handle chemical reactions using tabulated chemistry. This allows for discrete-exact sensitivity to be computed efficiently for arbitrary chemical mechanisms. Putting this together, DNS of a three-dimensional reacting round jet are performed at moderate Reynolds numbers. Sensitivity obtained from the adjoint solution is used to study flame and chemistry responses to turbulent flow actuation.