ABSTRACT

Turbulence models for passive scalar transport are known to have difficulties in complex flows involving strong rotation or MHD effects. Here, we consider the transport of a passive scalar in homogeneous turbulence examined in rotating frames. We first examine the effects of system rotation in the case of decaying hydrodynamic turbulence using Rapid Distortion Theory (RDT) as a guide. It is shown that the evolution of the scalar flux is strongly influenced by the structure dimensionality of the flow, and this suggests that scalar flux models must be made structure aware. Then, using Direct Numerical Simulations (DNS), we proceed to examine the case of passive scalar transport under the influence of homogeneous MHD turbulence in a conducting fluid that is undergoing mean shear in fixed and rotating frames. It is shown that in all the cases considered here, the evolution of the scalar flux coefficients can be explained in terms of the structural information provided by the one-point structure tensors. These results provide strong support for the formulation of structure-based models for passive scalar transport.