Progress on detached-eddy simulation of massively separated flows

One of the greatest challenges facing Computational Fluid Dynamics is in accurately calculating massively separated flows at high Reynolds numbers. In 1997, Spalart et al. [2] proposed Detached-Eddy Simulation (DES) with this challenge in mind. The method is a hybrid, combining Reynolds-averaged Navier Stokes (RANS) and Large Eddy Simulation (LES). DES combines the efficiency of Reynolds-averaged approaches in the boundary layer and the accuracy of the Large Eddy Simulation in separated regions. LES and therefore DES requires a time-accurate and three-dimensional solution. As grid densities are increased, more unsteady flow features are resolved. The need for time-accurate solutions on dense grids implies that high performance parallel computation can substantially enhance DES efforts. The DoD High Performance Computing and Modernization Office granted a Challenge project to research this topic. This manuscript summarizes the progress of the Challenge project, "Analysis of Pull Aircraft with Massive Separation Using Detached-Eddy Simulation". Numerous flows are examined, including a cylinder, two- and three-dimensional forebodies, a prolate spheroid, a supersonic base flow, a delta wing, a notional truck, the C130, the F-16, and the F-15E. All of the calculations described above are performed on structured and unstructured grids using a flow solver - Cobalt - which uses Message Passing Interface (MPI) for parallel solution. Calculations have been performed on a variety of high performance machines. Depending on the problem size, solutions are obtained on as many as 512 processors, providing full aircraft, unsteady solutions in approximately one day.