Large-Eddy and Wall-Modelled Simulations of Turbulent Flow over Two-Dimensional River Dunes

Publication date: Available online 17 November 2018Source: Physics and Chemistry of the Earth, Parts A/B/CAuthor(s): Mojtaba Mellati Nokhandan, Ugo Piomelli, Mohammad OmidyeganehAbstractTurbulence models based on the Spalart-Allmaras Detached-Eddy Simulation (DES) approach are used to compute the turbulent flow over a two-dimensional dune geometry. DES was developed for massively separated flows, but has been applied as a wall model to attached flows as well. In attached shear layers, however, the lack of resolved eddies in the region where the model switches from a turbulence model to a Subfilter-Scale (SFS) one, results in an underprediction of the wall stress, and a shift in the logarithmic layer. The dune studied here is neither a fully attached flow nor a massively separated one, and allows us to investigate the accuracy of DES wall-models in intermediate cases of this type. Results are compared to a well-validated LES database. DES based methods are found to be more accurate in this application, compared to attached boundary layers. All the methods required approximately 3% of the CPU time of the wall-resolved LES simulations. All methods gave similar results, but the Improved Detached Eddy Simulation seemed preferable because of the consistency of the trends it predicted.
Source: Physics and Chemistry of the Earth, Parts ABC - Category: Science Source Type: research