title: Large-scale anisotropy in stably stratified rotating flows.
abstract: We present results from direct numerical simulations of the Boussinesq equations in the presence of rotation and/or stratification, both in the vertical direction. The runs are forced isotropically and randomly at small scales and have spatial resolutions of up to 1024(3) grid points and Reynolds numbers of ≈1000. We first show that solutions with negative energy flux and inverse cascades develop in rotating turbulence, whether or not stratification is present. However, the purely stratified case is characterized instead by an early-time, highly anisotropic transfer to large scales with almost zero net isotropic energy flux. This is consistent with previous studies that observed the development of vertically sheared horizontal winds, although only at substantially later times. However, and unlike previous works, when sufficient scale separation is allowed between the forcing scale and the domain size, the kinetic energy displays a perpendicular (horizontal) spectrum with power-law behavior compatible with ∼k(⊥)(-5/3), including in the absence of rotation. In this latter purely stratified case, such a spectrum is the result of a direct cascade of the energy contained in the large-scale horizontal wind, as is evidenced by a strong positive flux of energy in the parallel direction at all scales including the largest resolved scales.
authors.affiliation: National Center for Atmospheric Research, P. O. Box 3000, Boulder, Colorado 80307, USA and Institute for Chemical-Physical Processes, Rende (CS), 87036, Italy and Space Sciences Laboratory, University of California, Berkeley, California 94720, USA.
authors.forename: R
authors.initials: R
authors.lastname: Marino
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: P D
authors.initials: PD
authors.lastname: Mininni
authors.affiliation: National Center for Computational Sciences, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Rosenberg
authors.affiliation: National Center for Atmospheric Research, P. O. Box 3000, Boulder, Colorado 80307, USA and Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: A
authors.initials: A
authors.lastname: Pouquet
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D004735:Energy Transfer; D005583:Fourier Analysis; D007700:Kinetics; D008962:Models, Theoretical; D012399:Rotation; D012996:Solutions
chemical_list: D012996:Solutions