Direct numerical simulation of BOLT hypersonic flight vehicle

The transition of a laminar to turbulent boundary layer for a high speed vehicles plays an important role in their design due to comparatively higher heat flux and skin friction drag from a turbulent vs. laminar boundary layer. The Boundary Layer Transition (BOLT) flight experiment aims to take the current understanding of this process to more complex geometries, building off of previous work from the HIFiRE program. For the BOLT geometry, due to complex geometric features, a range of instability mechanisms are expected which cause the laminar boundary layer to transition to a turbulent state. This complexity makes simplifying assumptions used in traditional stability analysis invalid on a practical level. In this paper we consider the computation of the BOLT geometry to understand and examine the complex flow features. To analyze the flow physics on this vehicle configuration we carry out Direct Numerical Simulation (DNS) at various Reynolds and Mach numbers and present highly resolved calculations of a steady realization of the flow field for which to perform stability analysis on in the future. We observe for lower Reynolds numbers that small amplitude distributed roughness does not introduce new flow structures but does increase the heat flux of the already present structures. For higher Reynolds numbers we observe the amplification of the stationary crossflow instability and a Mack mode like unsteady pressure disturbance.