Effect of a rear-attached splitter plate on the vortex dynamics and turbulence characteristics in a cylinder wake

This study investigates the influence of a rear-attached splitter plate on the vortex dynamics and turbulence characteristics in the wake of a circular cylinder. Three-dimensional direct numerical simulations (DNS) are performed at a turbulent Reynolds number of 1000 and non-dimensional plate lengths ( $ L/D$ ) of 0–4. The splitter plate affects the vortex dynamics and turbulence characteristics in a highly non-monotonic manner. Specifically, both the strength of the primary vortices and the turbulent kinetic energy in the wake decrease with increasing $ L/D$ over $ L/D$ = 0–1.5, followed by a local increase over $ L/D$ = 1.5–2 and another decrease over $ L/D$ ≥ 2. The abnormal local increase is because the vortex formation location transitions from downstream of the splitter plate for $ L/D$ ≤ 1.5 to the two sides of the plate for $ L/D$ ≥ 2. Owing to the presence of the primary vortex street in the wake, the turbulence in the wake is strongly anisotropic both globally and locally. After removing the contribution from the coherent primary vortices, the wake becomes much more isotropic globally and homogeneous locally. The present DNS dataset also enables an evaluation of several widely used surrogate models for the kinetic energy dissipation rate. A major finding is that a minor increase in the contribution of the coherent component (e.g. for $ L/D$ ≥ 2) may strongly deteriorate the applicability of the surrogate models of local axisymmetry and local homogeneity. In general, this study provides new insights and mechanisms for the control of turbulence in bluff-body wakes.