Characteristics of wake turbulence generated by a normal flat plate

Direct numerical simulations were performed to investigate the wake turbulence behind a thin normal flat plate. At Reynolds number 400, a low frequency modulation of the near wake was observed, resulting in a low-drag and high-drag regime. The low-drag regime was characterized by less coherent von Korman (V-K) vortices, while highly coherent V-K vortices were shed in the high-drag regime. Distinct flow structures were observed in the two drag regimes. Proper orthogonal decomposition (POD) was used to identify the dominant structures in the flow. It was observed that the low frequency modulation of the wake was captured by the third dominant POD mode. The statistical analysis was also performed to study the variation of Reynolds stresses and fluctuating kinetic energy in the wake. The statistical data were compared with a higher Reynolds number case of 1200. The comparison revealed that the near-wake flow is drastically different at these two Reynolds numbers, resulting in significant variation in the near-wake statistical quantities. However, at downstream locations, the variation in the quantities was observed to be both qualitatively and quantitatively similar.