Large Eddy Simulation of High-Reynolds-Number Free and Wall-Bounded Flows

The ability to simulate complex unsteady flows is limited by the current state of the art of subgrid-scale (SGS) modeling, which invariably relies on the use of Smagorinsky-type isotropic eddy-viscosity models. Turbulent flows of practical importance involve inherently three-dimensional unsteady features, often subjected to strong inhomogeneous effects and rapid deformation, which cannot be captured by isotropic models. Although some available improved SGS models can outperform the isotropic eddy-viscosity models, their practical use is typically limited because of their complexity. Development of more-sophisticated SGS models is actively pursued, and it is desirable to also investigate alternative nonconventional approaches. In ordinary large eddy simulation (LES) approaches models are introduced for closure of the low-pass filtered Navier–Stokes equations (NSE). A promising LES approach is the monotonically integrated LES (MILES), which involves solving the unfiltered NSE using high-resolution monotone algorithms; in this approach, implicit SGS models, provided by intrinsic nonlinear high-frequency filters built into the convection discretization, are coupled naturally to the resolvable scales of the flow. Formal properties of the effective SGS modeling using MILES are documented using databases of simulated free and wall-bounded inhomogeneous flows, including isotropic decaying turbulence, transitional jets, and channel flows. Mathematical and physical aspects of (implicit) SGS modeling through the use of nonlinear flux limiters are addressed using a formalism based on the modified LES equations.