  Statistically stationary and homogeneous shear turbulence (SS-HST) is
investigated by means of a new direct numerical simulation code, spectral in
the two horizontal directions and compact-finite-differences in the direction
of the shear. No remeshing is used to impose the shear-periodic boundary
condition. The influence of the geometry of the computational box is explored.
Since HST has no characteristic outer length scale and tends to fill the
computational domain, long-term simulations of HST are `minimal' in the sense
of containing on average only a few large-scale structures. It is found that
the main limit is the spanwise box width, $L_z$, which sets the length and
velocity scales of the turbulence, and that the two other box dimensions should
be sufficiently large $(L_x\gtrsim 2L_z$, $L_y \gtrsim L_z$) to prevent other
directions to be constrained as well. It is also found that very long boxes,
$L_x \gtrsim 2 L_y$, couple with the passing period of the shear-periodic
boundary condition, and develop strong unphysical linearized bursts. Within
those limits, the flow shows interesting similarities and differences with
other shear flows, and in particular with the logarithmic layer of wall-bounded
turbulence. They are explored in some detail. They include a self-sustaining
process for large-scale streaks and quasi-periodic bursting. The bursting time
scale is approximately universal, $\sim 20 S^{-1}$, and the availability of two
different bursting systems allows the growth of the bursts to be related with
some confidence to the shearing of initially isotropic turbulence. It is
concluded that SS-HST, conducted within the proper computational parameters, is
a very promising system to study shear turbulence in general.
