Inside a drop, at a viscosity ratio of 0.5

Creeping flow past a spherical drop whose surface is free to move. The outer streamlines are fore-and-aft symmetric, as every creeping flow is; the inner ones are a closed circulation, driven by the shear the outside applies to the interface. The interface itself is moving at 33 per cent of the free stream, which is what a rigid sphere forbids and is the whole of why the drag is lower.

2 essays call moving-surface. 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 moving-surface 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.