Relation of Large-scale motions with inlet blowing perturbations in turbulent wall-bounded flows*

Direct numerical simulations (DNS) were performed in a turbulent channel flow to demonstrate the role of upstream perturbations in controlling heat transfer downstream. Snapshot POD and 3D adaptive Gaussian filtering were used to separate energetic and spatially large-scale motions. These scales carry most of the Reynolds stresses and turbulent kinetic energy. It is shown that the blowing perturbations enhance wall heat transfer at 3D to 5D (where D is jet diameter) downstream of the jets; this is a direct consequence of the proliferation of coherent vortical structures. The large-scale motions which form horseshoe vortices create strong sweep events downstream of perturbations; thus, enhancing heat transfer by moving hot fluid from the wall to the outer flow.