Vorticity in shearing box simulations of two dynamically interacting vortices evolved with RBV2 (left column) and PLUTO (right column). The simulations were run on 512 × 512 zones with an extent of ﹩{\rm{\Delta }}R=0.04\,\mathrm{au}﹩ centered at R = 1 au with a sound speed c_s = 0.05. The PLUTO snapshots were produced at times of ﹩0.0,2.4,4.0\,6.0﹩, and 32.8, from top to bottom, while the RBV2 snapshots were produced at ﹩0.0,2.4,4.0\,6.0﹩, and 55.8, from top to bottom. Not only is the substructure that develops significantly different, but in RBV2 the vortices complete 14 orbits before merger, while in PLUTO they merge after seven orbits.