Kelvin's circulation theorem

Kelvin's circulation theorem states that for an ideal, incompressible, and non-viscous fluid moving in a steady environment without external forces, the total circulation around any closed loop moving with the fluid remains constant over time. In simpler terms, if you imagine a loop of fluid particles moving together, the "twist" or "rotation" of that loop doesn't change as it moves through the fluid, provided the conditions are ideal. This principle helps explain how certain flow patterns, like vortices, persist in a fluid without external influences, highlighting the conservation of rotational motion in such scenarios.