title: Passive scalar convective-diffusive subrange for low Prandtl numbers in isotropic turbulence.
abstract: In this Rapid Communication, we study the behavior of a strongly diffusive passive scalar field T submitted to a freely decaying, homogeneous and isotropic turbulence with eddy-damped quasinormal Markovian simulations. We present a new subrange located between the k(-17/3) inertial-diffusive subrange and the Kolmogorov wave number k(η). This subrange is generated by small-scale convection linked to k(η) that balances diffusion effects. Thus, we build a typical length scale k(CD)(-1) based on convection and diffusion and give an expression for the shape of the passive scalar spectrum in this subrange E(T)∼√[Pr]k(-11/3) using physical arguments. This result unifies two different theories coming from Batchelor [G. K. Batchelor, J. Fluid. Mech. 5, 113 (1959)] and Chasnov [J. Chasnov et al., Phys. Fluids A 1, 1698 (1989)] and explains results previously obtained experimentally.
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France and CNRS, UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors: A
authors: A
authors: Briard
authors: Sorbonne Universités, UPMC Univ Paris 06, UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France and CNRS, UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors: T
authors: T
authors: Gomez