DOI: 10.1615/TSFP4
SEPARATING THE EFFECTS OF WALL-BLOCKING AND NEAR-WALL SHEAR IN THE INTERACTION BETWEEN THE WALL AND THE FREE-SHEAR LAYER IN A WALL JET
ABSTRACT
The statistical characteristics of two plane jets, one developing along a real wall and the other along a frictionless wall (equivalent to a zero-shear, non-deformable free surface) are compared by way of highly-resolved LES solutions at computational conditions close to DNS. The aim is to distinguish between two types of interaction of the outer shear layer with the wall: one inviscid, arising from wall blocking, and the other, associated with the near-wall shear in the boundary layer. Results are presented for mean-flow properties, second moments and budgets thereof, and for integral length scale. The comparisons demonstrate that, while the boundary layer adds distinctive features to the near-wall region, associated with turbulence production redistribution and small-scale activity, the outer shear layer and its inviscid interaction with the wall are the dominant features. The effect of the outer layer, in particular the high level of diffusion of turbulence towards the wall, renders the boundary layer very different from a conventional near-wall shear layer.