Multiple helical modes of vortex breakdown

Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvin's problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets.