Dependence on Grid Reynolds number. The hyperviscosities shown correspond to Re = 0.002, 0.02, and 0.2 with respect to the velocity shear introduced by the Keplerian flow, calculated on the grid scale. The initial phase of growth occurs at Re  <  1, where it is seen that the amount of growth depends on the Reynolds number. Upon saturation, all simulations converge to the same level of enstrophy. A heavily aliased solution occurs for ν⁽³⁾ = 10^-21, where even a simulation seeded only with noise develops vortices. The same does not occur for the hyperviscosities shown, where finite amplitude perturbations were required. We usually use ν⁽³⁾ = 10^-17.