Horizontal motion of columnar vortices formed in rotating thermal convection

We investigated horizontal motion of columnar vortices, flow structures having coherence along the rotation axis, observed in rotating thermal convection by laboratory experiments. Thermochromic liquid crystals were employed to visualize and detect vortical structures in horizontal cross-sections with the parameters Ra = 1.0 × 10⁷ and Ta = 1.0 × 10⁷ - 1.0 × 10⁸. Two different size of cylindrical fluid layers filled with water (Pr ∼ 7) were used to investigate vortex motion under the condition with or without centrifugal force effect. The method to detect and track vortex motion we established made it possible to conduct long-time interval photographing, without obtaining velocity or vorticity fields. Thanks to this and the long time measurements O(10³ s), some statistical analyses to clarify the diffusive motion of columnar vortices had been achieved. Interesting characteristics of columnar vortices, such as generation, disappearance, merging, repellence, and limitation of lifetime, enable them to behave as like anomalous diffusion.