A three-dimensional numerical study of flow separation and reattachment on a blunt plate

Three-dimensional numerical simulation of the unsteady flow over a blunt plate held normal to a uniform stream has been carried out to study the physics of unsteady separation and reattachment. A finite-difference procedure is used with 32 spanwise grid cells. In comparison with previous two-dimensional results, it is observed that the inclusion of spanwise variations significantly improves the calculations and provides superior comparisons with experimental data. Mean turbulent quantities are calculated and found to be in good agreement with experiments. Instantaneous as well as statistical quantities describing the characteristic length and time scales of the large-scale structures are also presented. The calculations have also been able to capture the experimentally observed low-frequency unsteadiness of the separation bubble. In addition, a selective high-frequency shedding from the separated shear layer was found to occur with a period equal to that of the low-frequency unsteadiness.