Three-dimensional visualization of columnar vortices in rotating Rayleigh–Bénard convection

 To enrich the three-dimensional experimental details of vortex structures in rotating Rayleigh–Bénard convection, we established a technique visualizing three-dimensional vortex structures using scanning planar particle image velocimetry. Experiments were performed at fixed Rayleigh number, \(\hbox {Ra} = 1.0 \times 10^7\) and different Taylor numbers from \(\hbox {Ta} = 6.0 \times 10^6\) to \(1.0 \times 10^8\), corresponding to convective Rossby numbers from \(0.1 \le \hbox {Ro} \le 0.5\) at which gradual transition between vortical plumes and convective Taylor columns regime is observed. Stream function distributions calculated from horizontal velocity vector fields visualize the vortex structure formed in the regimes. As quantitative information extracted from the visualized structures, distances between vortices recognized on the distributions show a good agreement with that evaluated by a theory. With the accumulated planar stream function distributions and vertical velocity component calculated from the horizontal velocity vectors, the three-dimensional representations of vortices indicate that quasi-two-dimensional columnar vortices straighten in the vertical direction with increasing Ta.