Dynamic Large-Eddy Simulation Modeling for Transitional and Turbulent Hypersonic Flows in CREATE-AV Kestrel

The US Army has a need for time-accurate high-fidelity tools to simulate hypersonic aerothermodynamics. Currently the software developed and maintained within the CREATE-AV program, specifically Kestrel and the collection of solvers it employs, offers remarkable computation speed and robustness to users. However, the numerical stability of Kestrel is enabled by numerical dissipation, which makes time-accurate simulations challenging. Important phenomena such as ultrasonic hypersonic transitional waves or high-Reynolds-number compressible vortical turbulence are likely to be improperly captured. The goal of this STTR effort to address this gap. In the hypersonic regime, for slender geometries and low-to-zero angles of attack, longitudinal acoustic modes known as second-mode waves are the prominent transition mechanism. These waves operate in the ultrasonic regime (up to 1 MHz at high enthalpies), as such they are very sensitive to dissipative numerics, which in turn, are needed in the turbulent region. High-order spectral numerics can yield rapid grid convergence of second mode growth; however, they lack the robustness offered by lower-order calculations, such as the ones available in Kestrel, thus making it challenging to simulate time-accurate hypersonic flows. A recent breakthrough in Dr. Scalo's lab proved that is possible to capture the laminar-to-turbulent modal transition via a dynamic large-eddy simulations (LES) (or sub-filter-scale, SFS modeling) approach capable of preserving second-mode wave dynamics by applying dissipation only in the turbulent region. This achievement was made possible via the application of the dynamic LES model approach called Quasi-Spectral Viscosity, which, as demonstrated in a prior low-speed publication by, can be extended to non-spectral numerics such as the ones present in Kestrel. The latter approach was referred to as Coherent-vorticity Preserving dynamic Large-eddy simulation and its compressible extension will be the basis of the proposed STTR effort. HySonic proposes to assess the current performance of CREATE-AV Kestrel using a two datasets. High-fidelity simulation data from an in-house, block-spectral code (H3AMR), will be used in conjunction with data collected from a Mach-6 quiet tunnel at Purdue University. After assessing Kestrel's current capabilities, a novel dynamic LES model will be derived, tested, and implemented to extend Kestrel's hypersonic transition modeling capabilities.