# Fine vortex structure and flow transition to the geostrophic regime in rotating Rayleigh-B\'enard convection

## TL;DR

This study investigates vortex structures in rotating Rayleigh-Bénard convection, demonstrating the accuracy of asymptotic theory in the geostrophic regime and identifying a flow transition from weak to strong rotation.

## Contribution

It provides spatially-resolved measurements of vortex structures and compares them with theory, revealing the flow transition and extending understanding of rotation effects.

## Key findings

- Asymptotic theory accurately predicts vortex profiles in the geostrophic regime.
- Flow transition from weak to geostrophic convection is identified.
- Transition parameters align with previous heat-transfer scaling laws.

## Abstract

We present spatial-resolved measurements of the columnar vortex structures in rotating Rayleigh-B\'enard convection. The scaled radial profiles of the azimuthal velocity $u_{\phi}(r)$ and vertical vorticity ${\omega}(r)$ of the vortices are analyzed and compared with the predictions of the asymptotic theory. The results reveal that the asymptotic theory predicts accurately $u_{\phi}(r)$ and ${\omega}(r)$ in the geostrophic convection regime, but extension of the theory in the weak rotation regime is needed to interpret the rotation-dependence of the experimental data. Our measurements of the mean velocity, vorticity of the vortices, and the strength of the vortex shield structure all indicate a flow transition from weekly rotating convection to geostrophic convection. Results of the parameter values for the transition are in agreement with the scaling relationship obtained from previous heat-transfer measurements.