Routes to turbulent Taylor vortices: Vortex splitting and merging in chaotic state and the role of particles

A novel experimental finding of vortex splitting and merging (VSM) route to turbulence is reported in the counter-rotation regime of the Taylor–Couette flow of a Newtonian fluid, and the role of neutrally buoyant inertial particles on this transition pathway is analysed up to a particle volume fraction of phi equals 0.3 ϕ = 0.3 $\phi = 0.3$ over a range of rotation ratios negative 0.35 less than or slanted equals upper Omega equals omega Subscript o Baseline divided by omega Subscript i Baseline less than 0 − 0.35 ⩽ Ω = ω o / ω i < 0 $-0.35\leqslant \varOmega =\omega _o/\omega _i\lt 0$ (where omega Subscript i ω i $\omega _i$ and omega Subscript o ω o $\omega _o$ are the angular speeds of the inner and outer cylinders, respectively). The onset of VSM is found to coincide with the transition of a quasi-periodic state (‘doubly’ modulated wavy vortex [DMWV], characterised by two incommensurate frequencies) to a chaotic state (chaotic wavy vortex [CWV], in the background of VSM) at phi less than or slanted equals 0.15 ϕ ⩽ 0.15 $\phi \leqslant 0.15$ , giving rise to a new state of ‘VSM + CWV’ in which the VSM lives within a distinct CWV state. With further increasing particle loading, however, the VSM appears via MWV right arrow → $\to$ DMWV right arrow → $\to$ CWV Subscript normal upper B Baseline right arrow