High-fidelity simulation of laminar-to-turbulent transition in hypersonic boundary layer on a sharp cone

Laminar-to-turbulent transition in hypersonic boundary layer on a straight cone is numerically investigated in this study. High-fidelity simulation is performed with direct-numerical simulation (DNS) coupled with the linear stability theory (LST). This study focuses on the transition scenario of fundamental breakdown, driven by the two-dimensional Mack 2nd mode and a pair of oblique modes. The major instabilities in the hypersonic boundary layer are identified by LST and introduced at the DNS inlet. Current DNS computations successfully capture intrinsic transition phenomena, including aligned vortical structures and peak heat flux in the transition process, and complete transition to turbulent flow. Appropriate numerical dissipation associated with shock-capturing methods is investigated in this study because of the presence of a nose shock outside the boundary layer and compression waves from amplified instabilities inside the boundary layer. This numerical study is conducted with two shock sensors. A classical shock sensor generates excessive dissipation in the viscous boundary layer, which artificially delays the turbulent transition. The alternative sensor reduces the unintended dissipation, allowing flow to develop turbulence within the computational domain. Computational data are discussed with relevant experimental and theoretical data.