  We characterize the nature of thin, axisymmetric, inviscid, accretion flows
of cold adiabatic gas with zero specific energy in the vicinity of a black hole
by the specific angular momentum. Using two-dimensional hydrodynamic
simulations in cylindrical geometry, we present various regimes in which the
accretion flows behave distinctly differently. When the flow has a small
angular momentum $(\lambda\lsim\lambda_b)$, most of the material is accreted
into the black hole forming a quasi-spherical flow or a simple disk-like
structure around it. When the flow has a large angular momentum (typically,
larger than the marginally bound value, $\lambda\gsim\lambda_{mb}$), almost no
accretion into the black hole occurs. Instead, the flow produces a stable
standing shock with one or more vortices behind it and is deflected away at the
shock as a conical outgoing wind of higher entropy. If the flow has an angular
momentum somewhat smaller than $\lambda_{mb}$
$(\lambda_{u}\lsim\lambda\lsim\lambda_{mb})$, a fraction (typically, $5-10$\%)
of the incoming material is accreted into the black hole, but the the flow
structure formed is similar to that as for $\lambda\gsim\lambda_{mb}$. Some of
the deflected material is accreted back into the black hole, while the rest is
blown away as an outgoing wind. These two cases with $\lambda\gsim\lambda_u$
correspond those studied in the previous works by Molteni, Lanzafame, \&
Chakrabarti (1994) and Ryu \etal (1995). However, the flow with an angular
momentum close to the marginally stable value $(\lambda_{ms})$ is found to be
unstable. More specifically, if
$\lambda_b\lsim\lambda\sim\lambda_{ms}\lsim\lambda_u$, the flow displays a
distinct periodicity in the sense that the inner part of the disk is built and
