The flow is solenoidal by construction, which is what the law needs

The divergence of the double gyre, sampled along a line at three times. It is written as the curl of a stream function stated in closed form, so its divergence is zero analytically and at round-off numerically — which matters, because a field with a small divergence would change area at a small rate that could be mistaken for an integrator's error.

2 essays call kinematic-exact. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

It is also the blast radius. Changing kinematic-exact changes every figure listed here at once, and on this site it may change what they assert as well as what they show — which is what has to be rebuilt and looked at before the change is believed.