  Results are presented for one-dimensional numerical hydrodynamics
computations of the structure and evolution of Lya forest clouds
gravitationally confined by dark matter minihalos. The clouds are developed
from linear perturbations at high redshift and exposed to either a QSO- or
galaxy-dominated metagalactic radiation field at moderate redshifts. While the
emphasis is on spherical systems, slab symmetry is also considered. Three zones
may be identified in a collapsed cloud: (1) a quasi-hydrostatic core in thermal
equilibrium, (2) a nonhydrostatic intermediate zone out of thermal equilibrium,
and (3) a cosmological accretion layer joining onto the Hubble expansion. Most
of the measured Lya forest column densities arise in the intermediate zone. The
development of the core would result in a flattening in the column density
distribution near an HI column density of 10**15-10**16 cm**-2. The cloud
diameters corresponding to an HI column density of 10**14 cm**-2 lie in the
range 10-60 kpc, while systems with column densities exceeding 10**15 cm**-2
have diameters smaller than 10 kpc. Systems with circular velocities exceeding
50 km/s result in clouds which contract until they become Jeans unstable and
collapse. The critical column density for collapse is 10**17-10**18 cm**-2. A
mild correlation of Doppler parameter with neutral hydrogen column density is
found in several models for systems with column densities less than 10**13.5
cm**-2, with Doppler parameters occurring as low as b > 20 km/s for 10**13
cm**-2 column density systems. No lines with b < 15 km/s are found.
