The phase-averaged large-scale structures in three-dimensional turbulent wakes

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Abstract
Experiments are described which show that large-scale coherent structures exist in the wakes behind three-dimensional blunt bodies. Using a ‘flying hot-wire’ apparatus, the vortex-shedding cycle has been described by phase-averaged vector fields allowing an animation of large-scale motions to be produced. It is found that the large-scale structures retain their identity for long streamwise distances and contribute significantly to the Reynolds stress.Using critical-point theory as described recently by Perry, Lim & Chong (1980), the effect of phase ‘jitter’ on ‘washout’ has been analysed. Furthermore, it is found from critical-point theory that the large-scale motions possess the same geometrical features as the low-Reynolds number (unsteady laminar flow) wake results of Perry & Lim (1978) and Perry et al. (1980).