Almost horizontal turbulence

The paper is published without modifications. Kolmogorov's manuscript was apparently prepared during his participation in one of expeditions of the ship “D. Mendeleev” to the Atlantic Ocean (1969) or in a circumnavigation of the world (1971) organized by the Institute for Oceanology led at the time by A. S. Monin. As Kolmogorov himself wrote, the choice of the topic was stimulated by observations concerning “…meanders with horizontal sizes of hundreds of kilometers on a flow involving a layer of hundreds of meters, with subsequent disintegration of these meanders into vortices gradually decreasing in size to several kilometers.” In modern terminology, the paper is devoted to the problem of intensive mixing in pycnoclines, that is, thin layers of stratified fluid, caused by internal waves whose frequencies are less than the Brent–Väisälä frequency. Here I would like to note two circumstances. The first is the scientific insight characteristic for Kolmogorov; this very approach was later reflected in numerous publications (see, for instance, the monograph by V. S. Modevich, V. I. Nikulin, and A. G. Stetsenko “Dynamics of internal mixing in a stratified medium,” Institute for Hydromechanics, Academy of Sciences of Ukraine, Naukova Dumka, Kiev 1988). The second, the more significant in my opinion, is the genuine intellectual curiosity and breadth of thought of this great thinker, who studied not only the most abstract mathematical constructions but also got his head out of the clouds with great interest to solve concrete applied problems.