A laboratory investigation was conducted to quantify the influence of background rotation on nearly zero-mean turbulence generated within an off-axis mounted isotropic box. High-resolution particle image velocimetry measurements were performed at the box center under varying rotation rates to examine the onset and development of anisotropy. In the absence of rotation, the turbulence exhibits nearly isotropic behavior, with radial and azimuthal velocity fluctuations closely matched and energy spectra consistent with Kolmogorov scaling. As the inverse turbulent Rossby number, ${\text{Ro}}_{\varepsilon }^{-1}$, increases, spectral anisotropy becomes increasingly pronounced, and the range of scales over which the radial and azimuthal spectra diverge broadens. The lower bound of this anisotropic range follows the scaling $({\kappa }_L-{\kappa }_{DI})\eta ={\text{Ro}}_{\varepsilon }^{-1}/40$, indicating a progressive influence of the Coriolis effects. A generalized Taylor transformation applied to spatial and temporal spectra yields characteristic convection velocities $U_r^{*}$ and $U_{\theta }^{*}$, which exceed the local rms fluctuations and scale as $U_r^{*}\sim 3u_r^{\prime }$ and $U_{\theta }^{*}\sim 2u_{\theta }^{\prime }$. Direction-specific turbulent rotation numbers exhibit a linear dependence on ${\text{Ro}}_{\varepsilon }^{-1}$, linking integral-scale rotational dynamics to small-scale anisotropy. The results provide experimental support for theoretical predictions of energy redistribution, quasi-two-dimensionalization, and wave-eddy interaction in rotating turbulence. The empirical scalings may offer compact constraints for turbulence closures in noninertial frames and establish a basis for future studies of scalar transport and dispersion in geophysical and astrophysical flows.

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• Rotating turbulence
• Turbulence
• Particle image velocimetry