Generation of Turbulent In ow Data for Spatially-Developing Boundary Layer Simulations

2 A method for generating three-dimensional, time-dependent turbulent innow data for simulations of complex spatially-developing boundary layers is described. The approach is to extract instantaneous planes of velocity data from an auxiliary simulation of a zero pressure gradient boundary layer. The auxiliary simulation is also spatially-developing, but generates its own innow conditions through a sequence of operations where the velocity eld at a downstream station is rescaled and reintroduced at the inlet. This procedure is essentially a variant of the Spalart 1] method, optimized so that an existing innow-outtow code can be converted to an innow-generation device through the addition of one simple subroutine. The proposed method is shown to produce a realistic turbulent boundary layer which yields statistics that are in good agreement with both experimental data and results from direct simulations. The method is used to provide innow conditions for a large eddy simulation (LES) of a spatially-evolving boundary layer spanning a momentum thickness Reynolds number interval of 1530-2150. The results from the LES calculation are compared with those from other simulations that make use of more approximate innow conditions. When compared with the approximate innow generation techniques, the proposed method is shown to be highly accurate, with little or no adjustment of the solution near the inlet boundary. In contrast, the other methods surveyed produce a transient near the inlet that persists several boundary layer thicknesses downstream. Lack of a transient when using the proposed method is signiicant since the adverse eeects of innow errors are typically minimized through a costly upstream elongation of the mesh. Extension of the method for non-zero pressure gradients is also discussed.