Characteristics of the near wake region behind a cylinder at critical and super-critical Reynolds numbers

Large-eddy simulations (LES) of the flow past a circular cylinder are used to investigate the characteristics of the near wake region at Reynolds numbers Re = 2.5 × 105 - 8.5 × 105. This range encompasses both the critical and super-critical regimes. Wake characteristic lengths are measured and compared between the different Reynolds numbers. It is shown that the super-critical regime is characterised by a plateau in the drag coefficient at about CD ˜ 0.22, and a quasi-stable wake which has a width of dw /D ˜ 0.4. The analysis also shows a steep decrease in the Reynolds stresses when entering the super-critical regime. Furthermore, the overall analysis shows that after the changes occurring at critical Reynolds numbers, the wake enters a regime where its dynamics is quite similar regardless of the Reynolds number.