DOI: 10.1615/ICHMT.2015.THMT-15
ISBN Print: 978-1-56700-427-4
ISBN CD: 978-1-56700-428-8
Characteristics of the near wake region behind a cylinder at critical and super-critical Reynolds numbers
ABSTRAKT
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 dω/D ~ 0.4. Power spectra of the lift fluctuations are computed. Wake vortex shedding is found to occur for both regimes investigated, although a jump in frequencies is observed when the flow enters the super-critical regime. The analysis also shows a steep decrease in the fluctuating lift when entering the super-critical regime. Furthermore, the analysis of the turbulent statistics 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.