Abstract
Different transition to turbulence routes for the flow around blunt bodies
are possible. Non-modal amplification of perturbations via the lift-up effect
has recently been explored to explain transition near the stagnation point in
axisymmetric bodies. However, only perturbations already present in the
boundary layer can be amplified, and the mechanisms by which free-stream
perturbations enter the boundary layer have not yet been fully explored. In
this study, we present an investigation of how disturbances enter the boundary
layer via the stagnation point. This linear mechanism is expected to dominate
over non-linear mechanisms previously identified on the formation of boundary
layer perturbations at low turbulence intensity levels. A parametric
investigation is presented, revealing trends with Reynolds and Mach numbers.