  We study the large-scale helical vortex shedding regime in the wake of an
axisymmetric body with a blunt trailing edge at high Reynolds numbers, both
experimentally and by means of local, linear, spatiotemporal stability
analysis. In the instability analysis we take into account the detailed
downstream evolution of the basic flow behind the body base. The study confirms
the existence of a finite region of absolute instability for the first
azimuthal number in the near field of the wake. Such instability is believed to
trigger the large scale helical vortex shedding downstream of the recirculating
zone. Inhibition of vortex shedding is examined by blowing a given flow rate of
fluid through the base of the slender body. The extent of the locally absolute
region of the flow is calculated as a function of the bleed coefficient,
$C_b=q_b/(\pi R^2u_\infty)$, where $q_b$ is the bleed flow rate, $R$ is the
radius of the base and $u_\infty$ is the incident free-stream velocity. It is
shown that the basic flow becomes convectively unstable everywhere for a
critical value of the bleed coefficient of $C_b^*\sim 0.13$, such that no
self-excited regime is expected for $C_b>C_b^*$. In addition, we report
experimental results of flow visualizations and hot-wire measurements for
increasing values of the bleed coefficient. When a sufficient amount of base
bleed is applied, flow visualizations indicate that vortex shedding is
suppressed and that the mean flow becomes axisymmetric. The critical bleed
coefficient predicted by linear instability analysis is shown to fall within
the experimental values in the range of Reynolds numbers analyzed here.
