Breeze Gravity Current in a Uniform Flow of Air
M.V. Shokurov^{*}, N.Yu. Kraevskaya |
Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russian Federation |
^{*} e-mail: shokurov.m@gmail.com |
Abstract
Breeze circulation is often observed nearby the water basin coasts and usually accompanied by a background synoptic wind. One of the basic dynamically important components of the breeze circulation is gravity current. In the present paper the latter is used as the breeze simplified model. The theory of interaction of gravity current and a uniform synoptic wind are developed. The gravity current in the domain of infinite height in a stationary environment and environment with background flow was considered. To solve this problem the law of conservation of mass and universal property of the Froude number was used, which is true in the steady state.
It is shown that increase of a tail-wind is followed by growth of the gravity current velocity and decrease of its height. The opposite situation is observed at increase of a head wind: the current velocity reduces and its height increases.
Using a Taylor series expansion for small values of the background flow velocity a linear dependence of gravity current velocity on background flow velocity can be obtained. The factor determining the slope of the velocity of gravity current propagation on the background wind speed, which is equal 2/3, is a universal constant.
The theory explains the results of numerical simulation previously obtained by numerous authors. A physical interpretation of dependence of the height and velocity of the gravity current on the background flow velocity is presented.
Keywords
gravity current, numerical simulation, the Froude number.
DOI: 10.22449/1573-160X-2017-1-3-10