INSTABILITY OF SWIRLING ELECTROLYTE FLOWS DRIVEN ELECTROMAGNETICALLY

We present experimental results complemented with numerical simulations of a recently discovered instability observed in a free-surface flow driven by an azimuthal electromagnetic force in a thin annular layer of an electrolyte between two concentric cylindrical electrodes. The flow instability leads to the formation of travelling anticyclonic vortices near the external electrode. The vortices exist for long times once they appear. Experimental visualization of the flow using a tracer and thermographic images shows that the instability arises in both isothermal and non-isothermal conditions. Although multiple axisymmetric flow solutions can exist for the same set of governing parameters, a linear stability analysis indicates that only one of such solutions can potentially lead to azimuthally periodic vortex patterns observed in our experiments. Further, using a fully three-dimensional hybrid finite volume-spectral numerical method, the emergence of the instability is reproduced.