Examining turbulent length scales and flow correlations in a direct numerical simulation study of a hypersonic boundary layer flow produced by a uniform aspect ratio mesh using a high-resolution low dissipation massively parallel CFD code.

This work reports the initial analysis of a direct numerical simulation (DNS) of a hypersonic turbulent boundary layer (TBL). The simulation uses an aspect ratio unity mesh allowing the better-conditioned capture of flow structures near the wall in all coordinate directions. The focus of this work is on the spatial organization of the primitive variable fields, density, velocity energy, and pressure, across multiple scale ranges within the TBL. A particular emphasis is on the impact of the small-scale turbulent flow structures on the evolution of the larger turbulent scales, such as the ones modeled in a large-eddy simulation (LES) of a TBL. A discussion of the examined turbulent time-series data extracted from the DNS, taken at numerous points and spanwise lines in the configuration, i.e., the only homogeneous time-series data possible for this otherwise highly inhomogeneous flow. This analysis was then used to comment on the treatment of small-scale thermodynamic processes in various previously-developed subgrid-scale (SGS) models for compressible turbulent flows.