Numerical Study of Three-Dimensional Turbulent Flows

Book excerpt: Direct numerical and large-eddy simulations were used to perform numerical experiments' relevant to the cases of interest. We employ a plane-channel geometry and impose mean-flow perturbations by subjecung fully developed 2D Poiseuille flow to irrotational deformations andlor in-plane motion of the channel walls. The former corresponds to outer-layer strains induced in boundary layers by pressure gradients, the latter to sudden variations in the near-wall region, caused by either step changes in the surface conditions or the combination of an outer-layer change and the no-slip boundary condition. This combination allows the physics of a broad class of spatially developing wall shear layers to be duplicated with a temporally evolving channel flow. The temporal computations can be realized much more effectively than can simulations of a spatial boundary layer. providing a much more extensive study for a given cost. As a consequence. we can consider a wide variety of mean-flow perturbations. Moreover, since mean statistics for these flows satisfy a one dimensional unsteady problem that contains the essential features of the spatial flow, they provide an effident means of testing on%point dosure models.