Two offset orthogonal vortex tubes are initialized in a periodic cube.
This study uses 432 points in each direction. The kinematic viscosity is 1.0 x 10^-4 and Prandtl number 1.
The primary variables are abbriviated as follows:
d - Distance between vortex tube centers
r1 - Radius of vortex tube along x-axis (upper tube)
v1 - Velocity scale for vortex tube along x-axis (upper tube)
r2 - Radius of vortex tube along y-axis (lower tube)
v2 - Velocity scale for vortex tube along y-axis (lower tube)