  The flow past a bullet-shaped blunt body moving in a pipe is investigated
through global linear stability analysis (LSA) and direct numerical simulation
(DNS). A cartography of the bifurcation curves is provided thanks to LSA,
covering the range of parameters corresponding to Reynolds number $Re =
[50-110]$, confinement ratio $a/A = [ 0.01 - 0.92]$ and length-to-diameter
ratio $L/d = [ 2-10]$. Results show that the first bifurcation is always a
steady bifurcation associated to a non-oscillating eigenmode with azimuthal
wavenumber $m=\pm 1$ leading to a steady state with planar symmetry. For weakly
confined cases ($a/A<0.6$) the second bifurcation is associated to an
oscillating mode with azimuthal wavenumber $m=\pm 1$, as in the unconfined
case. On the other hand, for the strongly confined case ($a/A>0.8$), on
observes destabilization of non-oscillating modes with $|m| =2,3$ and a
restabilization of the $m=\pm1$ eigenmodes. The aspect ratio $L/d$ is shown to
have a minor influence for weakly confined cases and almost no influence for
strongly confined cases. DNS is subsequently used to characterize the nonlinear
dynamics. The results confirm the steady bifurcation predicted by LSA with
excellent agreement for the threshold Reynolds. For weakly confined cases, the
second bifurcation is a Hopf bifurcation leading to a periodic,
planar-symmetric state in qualitative accordance with LSA predictions. For more
confined cases, more complex dynamics is obtained, including a steady state
with $|m|=3$ geometry and aperiodic states.
