Linear disturbance transport and amplification on a hypersonic cone to assess tunnel noise contamination effects on transition*

Boundary-layer transition measurements in hypersonic wind tunnels are contaminated by noise generated on the tunnel walls which prescribe the free-stream disturbance environment. The level and nature of the free-stream disturbances seen in flight necessarily differs from that in the tunnel, making computational or theoretical estimates necessary. This talk aims to identify how different kinds of disturbances in the free-stream can be transported and amplified, linearly, to a nominal transition location. The Green’s function of the adjoint equations provides insight to the transport of arbitrary free-stream disturbance in a cost-effective way. The results identify the transition location’s domain of dependence and what kinds of disturbances are most effectively received from the free-stream. The Green’s function is used to compute the response in the boundary layer to notional tunnel and flight disturbance environments to compare transition in flight vs that in a tunnel.