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

¹ FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster - P.O. Box 1207 Nieuwegein, The Netherlands
² Control Systems Technology, Department of Mechanical Engineering - Eindhoven University of Technology P.O. Box 513, 5600 MB Eindhoven, The Netherlands
³ Fluid Dynamics Laboratory, Department of Applied Physics - Eindhoven University of Technology Eindhoven, The Netherlands
⁴ Dynamics and Control, Department of Mechanical Engineering - Eindhoven University of Technology Eindhoven, The Netherlands

^(a) m.lauret@tue.nl

Received: 9 September 2013
Accepted: 28 October 2013

Abstract

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.