  The phenomena of self-sustained shock wave oscillations over conical bodies
with a blunt axisymmetric base subject to uniform high-speed flow are
investigated in a hypersonic wind tunnel at Mach number $M = 6$. The flow and
shock wave dynamics are dictated by two non-dimensional geometric parameters
presented by the three length scales of the body, two of which are associated
with the conical forebody and one with the base. Time-resolved schlieren
imagery from these experiments reveals the presence of two disparate states of
shock wave oscillations in the flow, and allows for the mapping of unsteadiness
boundaries in the two-parameter space. Physical mechanisms are proposed to
explain the oscillations and the transitions of the shock wave system from
steady to oscillatory states. In comparison to the canonical single-parameter
problem of shock wave oscillations over spiked-blunt bodies reported in
literature, the two-parameter nature of the present problem introduces distinct
elements to the flow dynamics.
