Detached-Eddy Simulation

TLDR

Detached‑eddy simulation (DES) was introduced in 1997, has since gained a community of supporters and critics, and is now regarded as more capable than traditional RANS or LES for high‑Reynolds, massively separated flows, though its performance is sensitive to grid design and lacks a theoretical order of accuracy. This review examines compelling examples that demonstrate the visual and quantitative success of DES. The review also discusses the numerical requirements of DES, including gridding practices, coupling with various RANS models, wall‑modeling extensions, and advanced variants such as zonal and delayed DES.

Abstract

Detached-eddy simulation (DES) was first proposed in 1997 and first used in 1999, so its full history can be surveyed. A DES community has formed, with adepts and critics, as well as new branches. The initial motivation of high–Reynolds number, massively separated flows remains, for which DES is convincingly more capable presently than either unsteady Reynolds-averaged Navier-Stokes (RANS) or large-eddy simulation (LES). This review discusses compelling examples, noting the visual and quantitative success of DES. Its principal weakness is its response to ambiguous grids, in which the wall-parallel grid spacing is of the order of the boundary-layer thickness. In some situations, DES on a given grid is then less accurate than RANS on the same grid or DES on a coarser grid. Partial remedies have been found, yet dealing with thickening boundary layers and shallow separation bubbles is a central challenge. The nonmonotonic response of DES to grid refinement is disturbing to most observers, as is the absence of a theoretical order of accuracy. These issues also affect LES in any nontrivial flow. This review also covers the numerical needs of DES, gridding practices, coupling with different RANS models, derivative uses such as wall modeling in LES, and extensions such as zonal DES and delayed DES.