Numerical Study of a Separated-Reattached Flow on a Blunt Plate

Large-eddy simulation (LES) of transitional separatingreattaching flow on a flat plate with a blunt leading edge has been performed. The Reynolds number based on the uniform inlet velocity and the plate thickness is 6.5103. A dynamic subgrid-scale model is employed in the transitional flow case. The LES results compare reasonably well with the available experimental data. The entire transition process has been visualized by using the LES data, and large-scale vortical structures have been observed at different stages of transition. It is known that different vortex shedding frequencies exist, especially the so-called low-frequency flapping when there is a separation bubble. It is not clear whether all transitional and turbulent separatingreattaching flows have different vortex shedding frequencies. It is also not clear what the working mechanisms are behind the so-called low-frequency flapping as reported widely. These issues are addressed.