Reynolds number dependency in supersonic spatially-developing turbulent boundary layers via DNS*

Direct Numerical Simulation (DNS) of compressible spatially-developing turbulent boundary layers (SDTBL) is performed at a Mach number of 2.5 and low/high Reynolds numbers over isothermal Zero-Pressure Gradient (ZPG) flat plates. Turbulent inflow information is generated by a dynamic rescaling-recycling approach (J. Fluid Mech., 670, pp. 581-605, 2011), which avoids the use of empirical correlations in the computation of inlet turbulent scales. The range of the low Reynolds number case is approximately 400-800, based on the momentum thickness, freestream velocity and wall viscosity. DNS at higher Reynolds numbers (about six times larger) is also carried out with the purpose of analyzing the effect of Reynolds number on the thermal transport and on the Morkovin’s Strong Reynolds Analogy (SRA) in the supersonic regime. Additionally, low/high order flow statistics are compared with DNS of an incompressible isothermal ZPG boundary layer at similar low Reynolds numbers and temperature considered as a passive scalar. Focus is given to the assessment of Reynolds number and compressibility effects on the dynamics of turbulent coherent structures.