  We report on a three-dimensional direct numerical simulation study of flow
structure and heat transport in the annular centrifugal Rayleigh-B\'{e}nard
convection (ACRBC) system, with cold inner and hot outer cylinders corotating
axially, for the Rayleigh number range Ra $ \in [{10^6},{10^8}]$ and radius
ratio range $\eta = {R_i}/{R_o} \in [0.3,0.9]$. This study focuses on the
dependence of flow properties on the radius ratio $\eta$. The temperature and
velocity fields reveal that different curvatures of the inner and outer
cylinders of the ACRBC system lead to asymmetric movements of hot and cold
plumes under the action of Coriolis force, resulting in the formation of zonal
flow. The physical mechanism of zonal flow is verified by the dependence of the
drift frequency of the large-scale circulation rolls and the space- and
time-averaged azimuthal velocity on $\eta$. We find that the larger $\eta$ is,
the weaker the zonal flow becomes. We show that the heat transport efficiency
increases with $\eta$. It is also found that the bulk temperature deviates from
the arithmetic mean temperature and the deviation increases as $\eta$
decreases. This effect can be explained by a simple model that accounts for the
curvature effects and the radially-dependent centrifugal force in ACRBC.
