Experimental stabilisation of 2D vortex patterns using time-dependent forcing

Experimental results of the effect of time-periodic and "chirped" (electro-magnetic) forcing on vortex patterns in shallow-water-layer flows are presented. Analogously to vibrational control, the use of a time-periodic forcing results in stabilisation of otherwise unstable vortex patterns. Chirped frequency forcing yields self-organising patterns that are different from those in stationary and periodically forced experiments. The results are shown to be consistent with theoretical analysis of 2D Taylor-Green vortices, i.e. unstable analytical solutions of the 2D Navier-Stokes equation. These results imply that, compared to the more often analysed stationary forced flows, time-varying forcing can stabilise different vortex patterns in shallow-water-layer flows.