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Título : | 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 |
Autor : | Dejoan, A. Leschziner, M. |
Palabras clave : | turbulent wall jet |
Fecha de publicación : | 5-ene-2006 |
Editorial : | Physics of Fluids, American Institute of Physics |
Resumen : | The statistical and structural characteristics of two plane jets, one developing along a real wall and
the other along a frictionless wall 共equivalent to a zero-shear, nondeformable free surface兲 are
compared by way of highly resolved LES 共large eddy simulation兲 solutions at computational
conditions close to those of DNS 共direct numerical simulation兲. The aim is to distinguish between
two types of influence of the wall on the outer shear layer: 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, structural characteristics, and the
integral length scale. The comparisons demonstrate that the wall affects a significant proportion of
the outer shear layer to a depth of approximately 3 times the thickness of the boundary layer, with
or without wall shear. Outside the immediate near-wall layer, in the interaction region, the influence
of the wall is affected by an interplay between turbulence diffusion toward the wall and inviscid
processes associated with pressure fluctuations and their reflection from the wall. The addition of
shear modifies substantially the statistical behavior and structure within the thin sheared region. The
state of anisotropy and the energy-redistribution process among the normal-stress components
change drastically, the structure is dominated by small scale, elongated eddies, and the near-wall
layer is observed to ‘shield’ the wall from the penetration of large-scale vortices from the outer shear
layer. The role of diffusion, in particular, renders the near-wall shear layer very different from a
conventional equilibrium boundary layer, its integral scale being considerably enhanced by the
influence of large-scale eddies originating in the outer shear layer and migrating toward the wall. |
URI : | http://documenta.ciemat.es/handle/123456789/2177 |
Aparece en las colecciones: | Artículos de Energía
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