Effects of Off-axis Rotation on Energy Transfer Mechanism of the Isotropic Turbulence

Turbulent flows in rotational systems have significant applications across diverse fields, spanning from large scales such as climate and oceanic systems to small scales such as turbomachinery. Previous experimental studies have primarily focused on homogenous turbulence and the rotational effect on the mean flow, while computational research tried to modify the existing turbulent models developed in inertial coordinates. There is a lack of understanding of the rotational effects on the energy transfer mechanism of turbulence as well as turbulent models directly developed in non-inertial coordinates. With PIV measurements applied on a zero-mean isotropic turbulent flow, the anisotropy between radial, tangential, and axial direction, induced by the presence of centrifugal force and Coriolis force, is investigated with a variety of statistics of turbulence. A Coriolis transportation mechanism is identified as a TKE transfer between radial and tangential directions, which may break the isotropic state of turbulence. This Coriolis transportation is quantified with PIV data experimentally and compared with other TKE terms to evaluate the rotational effect as well as provide a new perspective for modeling rotating turbulence.