Forced vortex merging and splitting events in ferrofluidic Couette flow

Time-dependent boundary conditions are ubiquitous in numerous natural and industrial flows. However, to date, the influence of such temporal modulations has been given minor attention. This research addresses ferrofluidic Couette flow between co-rotating cylinders a spatially homogeneous magnetic field subject time-periodic modulation. Using modified Niklas approximation, we study effect amplitude frequency modulation onto transition scenarios different toroidal structures, non-propagating vortex (nV) states, via merging splitting. Thereby, system response appears be quite sensitive/dependent on driving ΩH, which can cause notable “delay” response. Further, as result inertia ferrofluid, resisting fast-changing accelerating Kelvin force, new, nV states appear within an alternating field. These unstable under static fields. Finally, show that same state, while keeping similar dynamics, large discrepancies angular momentum torque observed.