Precursors of backflow events and their relationship with the near-wall self-sustaining process
Byron Guerrero, Martin F Lambert, Rey C Chin
JOURNAL OF FLUID MECHANICS | CAMBRIDGE UNIV PRESS | Published : 2021
This study examines the precursors and consequences of rare backflow events at the wall using direct numerical simulation of turbulent pipe flow with a high spatiotemporal resolution. The results obtained from conditionally averaged fields reveal that the precursor of a backflow event is the asymmetric collision between a high- and a low-speed streak (LSS) associated with the sinuous mode of the streaks. As the collision occurs, a lifted shear layer with high local azimuthal enstrophy is formed at the trailing end of the LSS. Subsequently, a spanwise or an oblique vortex spontaneously arises. The dominant nonlinear mechanism by which this vortex is engendered is enstrophy intensification due..View full abstract
This work was supported with supercomputing resources provided by the Phoenix HPC service at the University of Adelaide. This research was also undertaken with the assistance of resources provided at the NCI NF through the Computational Merit Allocation Scheme, supported by the Australian Government and the Pawsey Supercomputing Centre, with funding from the Australian Government and the Government of Western Australia. The authors acknowledge the financial support of the Australian Research Council.