When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating thermal convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely distributed vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being proportional ( ≈ 30%) to the cluster length. Such long-range correlation leads to the counterintuitive collective outward motion of warm vortices. Our study brings insights into the vortex dynamics that are widely present in nature.

当流体系统受到强烈旋转时，会发生离心流体运动，即密度较大（较轻）的流体会从（朝向）旋转轴向外（向内）移动。在这里，我们通过实验和数值证明了在旋转热对流中温暖和较轻的涡流的意外向外运动的存在。当离心浮力足够强以在涡度场中引起对称破坏时，这种异常涡旋运动发生在快速旋转下，即冷反气旋的涡度超过暖气旋的涡度。我们表明，通过流体动力学相互作用，密集分布的涡流可以自聚集成连贯的簇，并在这种流态中表现出集体运动。有趣的是，簇内涡旋速度波动的相关性是无标度的，相关长度与簇长度成正比（≈ 30%）。这种长程相关性导致暖旋涡违反直觉的集体向外运动。我们的研究为自然界中广泛存在的涡旋动力学提供了见解。