The vorticity (left), dimensionless entropy ﹩{ \mathcal S }=(s-{s}_{0})/{c}_{V}=\mathrm{ln}(p/{\rho }^{-\hat{\gamma }})﹩ (middle) and both quantities overlaid (right) at t = 2.5R_NS/c in runs Wig0532 and sigma100. The simulation with perturbed background develops strong shear at the boundary of the fragmented shock patches and along the shocks themselves. In simulation sigma100 with uniform background dipole, the vorticity peaks only along the shock. Entropy is generated at the shock in both cases, and appears around the boundaries of the shock patches in simulation Wig0532 as a result of the shifting position of the shock.