Large eddy simulation and turbulence control

Abstract

This paper reviews LES met hods, based on the; dynamic subgrid-scale model, that greatly improve the efficiency of turbulence control simulations in the context of drag reduction for plane turbulent channel flow. We begin by performing simulations of opposition control at Reynolds numbers in the range Reπ = I(M) to 590 which demonstrate a decrease in effectiveness of this control strategy with increased Reynolds number. We then review techniques for optimal control of turbulent flows and discuss our implementation using an instantaneous control framework where the flow sensitivity is computed from the adjoint LES equations. Detailed optimal control results are presented that demonst rate excellent agreement wit h available DNS at a fraction of the computational expense. Given the added efficiency of LES, a receding horizon control framework is also explored that results in increased drag reduction along with improved control distributions. Results are also presented for a hybrid LES/DNS method where optimization is performed using LES but the flow is advanced using DNS. This approach demonstrates that even coarse grid LES can serve as a viable reduced order model for DNS. In our ongoing efforts to seek greater model reductions for predictive control, we also explore the influence; of control on the basis functions obtained from proper orthogonal decomposition. © 2000 by Rice University.