  Viscous flow past a finite plate which is impulsively started in direction
normal to itself is studied numerically using a high order mixed finite
difference and semi-Lagrangian scheme. The goal is to resolve details of the
vorticity generation at early times, and to determine the effect of viscosity
on flow quantities such as the core trajectory and vorticity, and the shed
circulation. Vorticity contours, streaklines and streamlines are presented for
a range of Reynolds numbers $Re \in [250, 2000]$ and a range of times $t \in[0.
0002, 5]$. At early times, most of the vorticity is attached to the plate. The
paper proposes a definition for the shed circulation at early as well as late
times, and shows that it indeed represents vorticity that separates from the
plate without reattaching. The contribution of viscous diffusion to the
circulation shedding rate is found to be significant, but, interestingly, to
depend only slightly on the value of the Reynolds number. The shed circulation
and the vortex core trajectories follow scaling laws for inviscid self-similar
flow over several decades in time. Scaling laws describing the core vorticity,
core dissipation, boundary layer thickness, drag and lift forces in time and
Reynolds number are also presented. The simulations provide benchmark results
to evaluate, for example, simpler separation models such as point vortex and
vortex sheet models.
