Numerical simulation of gravity current propagation in a compressible atmosphere
M.V. Shokurov, N.Yu. Germankova |
Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russian Federation |
E-mail: shokurov.m@gmail.com, loogaru9@rambler.ru |
Abstract
Gravity current is one of the components of sea breeze circulation. For investigation of sea breeze circulation propagation of a gravity current in the atmosphere is numerically modeled using a two-dimensional hydrodynamic model allowing for compressibility. The result consists in a detailed description of development and propagation of a gravity current at the stage when the front speed is constant. Characteristic features of the structure of gravity current – front, «head», Kelvin-Helmholtz vortices − are noted. The dynamic characteristics of gravity current such as propagation velocity of front, current height, buoyancy deficit in the gravity current are determined. The dependence of the flow dynamic characteristics upon two following parameters is studied: the initial difference between potential temperatures of the cold air pool and the environment, and the initial height of the cold pool. Dimensionless front velocity (Froude number Fr) is calculated by three methods using characteristic heights of the current “head” and “body” which is located behind the “head”, and the cold pool initial height. The calculations show that in the first approximation Fr calculated from the gravity flow height, is actually a universal constant approximately equal to 1. More detailed analysis shows that Fr and the gravity current height are weakly dependent upon the ratio between the cold pool initial height and the atmosphere thickness. The conclusion is consistent with the results of other studies.
Keywords
gravity current, numerical simulation, Froude number.
DOI: 10.22449/1573-160X-2015-4-53-65