Simplified diagram of a gas centrifuge used for uranium isotope separation with a countercurrent circulation for increased separation.
The current in this example is induced by the bottom (waste) scoop, and the product scoop is behind a baffle, which is attached to and rotates with the rotor, to prevent it setting up equal but opposite current. The uranium diffuses across the radius of the rotor, with 238U migrating to the periphery and 235U to the centre. The countercurrent then concentrates the 238U to collect at the bottom (this is the waste or tail stream), and the 235U to collect at the top (product stream).
By baffling the bottom scoop, the inverse can be achieved (some diagrams show this instead), with 235U collecting at the bottom. Some designs also use heating to drive the countercurrent.

The bellows are slightly flexible and allow the rotor to be operated at speeds that would otherwise be supercritical.
Own work
Inductiveload