Influence of wall temperature on supersonic turbulent boundary layer development over concave surface geometries

Unsteady 3D compressible turbulent boundary layers evolving in the streamwise direction are inherently non-homogeneous and pose major challenges for Direct Numerical Simulation (DNS) due to: (i) full turbulence spectrum resolution, (ii) accurate time-dependent inflow turbulence, and (iii) compressibility effects. Wall-curvature-induced pressure gradients further intensify the complexity. This study presents DNS results of supersonic spatially-developing turbulent boundary layers (SDTBL) over a concave surface with a curvature ratio of δ/R ≈ -0.083 at Mach 2.86, relevant to high-speed aerospace systems such as scramjets and reentry vehicles. The wall geometry replicates the experimental setup of Donovan et al. (JFM, 259, 1994), and turbulent inflow conditions are extracted from a precursor flat-plate DNS. Simulations are conducted with high spatial and temporal resolution. Results offer detailed insight into turbulent transport mechanisms under strong Adverse Pressure Gradient (APG) induced by concave curvature, across a range of wall thermal boundary conditions: cold, adiabatic, and hot. A very strong correlation has been observed between attracting manifolds and Q2 (ejections) in a three-dimensional Lagrangian Coherent Study (LCS) analysis. Furthermore, centrifugal forces enhance spanwise flow variations and Q1/Q3 events in the supersonic concave wall and downstream, which cause positively correlated u’ and v’ fluctuations.