Dynamics of Layered Structures in the Final Stage
of Turbulence Decay in a Stably Stratified Fluid

A. V. Galaktionov* and V. S. Maderich**

* Institute of Fluid Mechanics, National Academy of Sciences of Ukraine, ul. Zhelyabova 8/4, Kiev, 252057 Ukraine

** Institute of Problems of Mathematical Machines and Systems, National Academy of Sciences of Ukraine,
pr. Akademika Glushkova 42, Kiev, 252187 Ukraine
E-mail: vlad@maderich.pp.kiev.ua

Received March 31, 1998; in final form, January 19, 1999

Abstract—The dynamics and energetics of layered structures in the final stage of turbulence decay in a stably
stratified fluid are considered. Such buoyancy-driven motions are distinguished together with internal waves
and quasi-horizontal vortices. Layered structures exist at small inner Froude and Reynolds numbers and large
Prandtl (Schmidt) numbers. The interaction between layered structures is studied numerically with the use of
the pseudospectral method. The rearrangement of the density field between structures is of importance in this
process. The transformation of a single patch in the field of a horizontal vortex is studied. It is shown that this
transformation involves three stages. In the first stage, the patch is curved into a spiral by the vortex. Thereafter,
the spiral branches coalesce under the effects of collapse, rearrangement of the density field between them, and
diffusion. In the final stage, the patch rotates with the vortex as a rigid body.

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