Assessment of inflow boundary conditions for compressible turbulent boundary layers

A description of different inflow methodologies for turbulent boundary layers, including validity and limitations, is presented. We show that the use of genuine periodic boundary conditions, in which no alteration of the governing equations is made, results in growing mean flow and decaying turbulence. Premises under which the usage is valid are presented and explained, and comparisons with the extended temporal approach [T. Maeder, N. A. Adams, and L. Kleiser, Direct simulation of turbulent supersonic boundary layers by an extended temporal approach, J. Fluid Mech. 429, 187 (2001)] are used to assess the validity. Extending the work by Lund [J. Comput. Phys. 140, 233 (1998)], we propose an inflow generation method for spatial simulations of compressible turbulent boundary layers. The method generates inflow by reintroducing a rescaled downstream flow field to the inlet of a computational domain. The rescaling is based on Morkovin's hypothesis [P. Bradshaw, Compressible turbulent shear layers, Annu. Rev. Fluid Mech. 9, 33 (1977)] and generalized temperature-velocity relationships. This method is different from other existing rescaling techniques [S. Stolz and N. A. Adams, Large-eddy simulation of high-Reynolds-number supersonic boundary layers using the approximate deconvolution model and a rescaling and recycling technique, Phys. Fluids 15, 2398 (2003); G. Urbin and D. Knight, Large-eddy simulation of a supersonic boundary layer using an unstructured grid, AIAA J. 39, 1288 (2001)], in that a more consistent rescaling is employed for the mean and fluctuating thermodynamic variables. The results are compared against the well established van Driest II theory and indicate that the method is efficient and accurate. (C) 2004 American Institute of Physics.