Direct Numerical Simulation of a Hypersonic Turbulent Boundary Layer over a Blunt Ogive

This study presents high-fidelity direct numerical simulation (DNS) of a cold-wall turbulent boundary layer over a blunt ogive at a nominal freestream Mach number of $5$ and a unit Reynolds number of $Re_u=27.9\times 10^6$/m. The blunt ogive geometry and the flow conditions of the DNS matched those measured in the Texas A\&M Hypervelocity Expansion Tunnel. In the DNS, long streamwise domains are used to simulate the spatial evolution of the turbulent boundary layer on the ogive surface. The study confirms that the use of very long streamwise domains of at least $\mathcal{O}(60-70\delta_i)$ (with $\delta_i$ being the inflow boundary-layer thickness) is required for the turbulence of the boundary layer to recover from the initial transient due to the digital-filtering (DF) inflow turbulence generation technique and achieve a fully developed state towards the latter part of the ogive. At the end of the ogive, the friction Reynolds number reaches as high as $Re_\tau \simeq 1100$, providing a unique hypersonic turbulence field in the high Reynolds number, cold-wall regime that is simultaneously subject to a favorable pressure gradient. Further comparisons with Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) results by Morreale et al. (AIAA Paper 2023-0455) for the same flow conditions and ogive geometry reveal that implicit LES reproduces wall pressure spectrum that closely matches DNS across low- and intermediate frequency ranges. Among the various RANS and LES approaches, only the Shear Stress Transport (SST) RANS model successfully reproduces both wall shear stress and surface heat flux.