spiral line; vortex line; circumvolution
Technical term in fluid dynamics and geometry. Refers to a line that forms a spiral or vortex pattern, or the act of winding around a center.
In fluid dynamics, a vortex line is defined as a curve tangent to the vorticity vector.
This figure draws a complex spiral line.
Compound of 渦 (ka, 'whirlpool, vortex') and 線 (sen, 'line'). The reading かせん follows standard on'yomi. The term is a modern technical coinage.