| Popis: |
Results from direct numerical simulation (DNS) of Reτ=390 channel flow subjected to the strain and deceleration typical of adverse pressure gradients (APGs), to the point of skin-friction reversal, are the reference for comparing four simple turbulence models. The statistics satisfy a one-dimensional unsteady problem and contain many of the physical complications associated with APGs, thus allowing a straightforward but nontrivial assessment of the models for APG flows, with rigorously defined boundary and initial conditions and an acceptable Reynolds number. We find the model accuracy varies significantly, with the Spalart–Allmaras and Menter SST schemes giving the best overall agreement with DNS. The other two models tested (Baldwin–Lomax and Launder–Sharma) deviate from the DNS, in terms of skin friction, much the same way they do in actual spatially developing APG boundary layers. This supports the relevance of the strained-channel idealisation. The DNS results are used to examine fundamental assumptions of the four models, casting light on the relative strengths and weaknesses of each. |
Full Text from ScienceDirect