tea leaf paradox

English

The tea leaves collect in the middle and the bottom, instead of along the rim.

The blue line is the secondary flow that pushes the tea leaves to the middle of the bottom.

Proper noun

the tea leaf paradox

1. (fluid dynamics) The phenomenon whereby tea leaves in a cup of tea migrate to the center and bottom of the cup after being stirred (due to friction towards the bottom), rather than being forced to the edges, as would be expected in a spiral centrifuge.