Is Isotropic Turbulent Diffusion Symmetry Restoring?

Analytic expressions of the convection diffusivity tensor in fully developed isotropic turbulent flow are given and used to evaluate the broadening of a cloud of marked particle pairs perpendicular and longitudinal with respect to an initial separation. Both turn out to remain different because of the difference between 〈v_⊥²〉 and 〈v_∥²〉. Parameter-free expressions for the variances σ_⊥ and σ_∥ yield the dependence on the Reynolds number and other flow parameters in addition to the known scaling behavior ∝τ^3-γ.