Influence of vorticity alignment upon scalar gradient production in three-dimensional, isotropic turbulence

We use a stochastic Lagrangian model to investigate how the mechanisms of scalar gradient production may be affected by alignments of vorticity with respect to strain principal axes. The most intense scalar gradient production occurs when vorticity aligns with the 'intermediate' strain eigenvector. Mean production conditioned on vorticity aligning with the extensional eigenvector is closer to mean production in the total flow. These differences are explained by the special statistics of both strain eigenvalues and scalar gradient alignment when vorticity aligns with a strain eigenvector.