Hypersonic Boundary Layer Transition of the BoLT-2 Flowfield at Flight Conditions

Boundary layer disturbances in the Boundary Layer Turbulence (BoLT-2) flowfield are investigated using a high-order, low-dissipation numerical method. DNS solution is forced with a freestream disturbance function to mimic the effects of freestream turbulence to obtain a response that reveals the most unstable transition mechanisms contributing to elevated heat transfer rates. Modal decomposition analysis is applied to datasets obtained from high-fidelity computations to reveal the relevant transition mechanisms potentially contributing to transition in flight. This is motivated by the fact that disturbance environments of ground test facilities initiates transition at lower Reynolds number conditions than flight on BoLT-2. Therefore, this work reveals the dominant transition mechanisms contributing to the transition process when introducing freestream disturbances under flight conditions. Modal analysis is performed with Spectral Proper Orthogonal Decomposition (SPOD) to reveal modes associated with significant disturbance amplification in regions of physical instability.