On the Use of Les with a Dynamic Subgrid-scale Model for Optimal Control of Wall Bounded Turbulence

This paper presents techniques for optimal control of turbulent flows based on the dynamic subgrid-scale LES model. This control scheme has been implemented using a finite time-window approach where the flow sensitivity is computed from the adjoint LES equations. LES results for optimal control of terminal turbulent kinetic energy are compared to Direct Numerical Simulation (DNS) under similar conditions. These comparisons indicate that optimal control based on LES can relaminarize low Reynolds number turbulent channel flow similar to results obtained using DNS but with significantly lower computational expense. Results are also presented for a novel hybrid LES/DNS scheme in which the optimization iterations are performed using LES while the flow is advanced in time using DNS. These hybrid simulations retain the computational efficiency of LES and the accuracy of DNS. Results from hybrid simulations clearly demonstrate that the controls computed based on LES optimization are also viable in the context of DNS. In all cases, the agreement between LES, DNS, and hybrid LES/DNS indicates that reliable turbulence control strategies can be efficiently developed based on LES.