Structure And Energy Of Turbulence Of JetCurrents In The River Mouths

Abstract

The turbulent structure of jet currents in the river mouths is conditioned by a number of specific features related mainly to attenuation of the runoff jet flow with its distance from the mouth, as well as with density stratification, and involvement of the sea/lake water mass in the jet movement. As a result of filed measurements in the Jordan River (Lake Kinneret, Israel) and The Kura River (Caspian Sea) mouths, the following conclusions have been made: The kinetic energy of the forward motion of the river flow is rapidly transforming into the energy of turbulence. In the eddy zones at the jet boundaries, the highest fluctuations of all three-velocity components are observed, as well as their commensurability. Dissipation of energy at first decreased in the section before the river mouth bar; then it increased along the flow due to significant hydraulic resistance at the bar and the jet boundaries. The generation of energy has two maximums: the first one was in the initial section of the river jet at its discharge into the lake, and the second one in the last section, in the zone of the full attenuation of the runoff flow. With the distance from the mouth along the river jet, linear dimensions of the turbulent eddies and the relationships between their scales (linear, lu, transversal, lw, and vertical, lv) undergo changes. Before the bar we observe the relationship lu<lw, while beyond the bar lu<<lw, which is attributed to the formation of large-scale turbulent eddies with a vertical axis of rotation. Farther beyond the bar, where the eddies collapse, the relationship lu ≈ lw ≈ lv is established.