Автор работы: Пользователь скрыл имя, 21 Октября 2011 в 10:38, реферат
Задача моделирования загрязнения воздуха состоит в оценке концентрации загрязняющих веществ в воздухе вне помещений, вызванной, например, ростом промышленного производства, случайными выбросами или движением транспорта. Моделирование загрязнения воздуха используется для установления общей концентрации загрязняющего вещества, а также для выяснения причины необычно высоких ее уровней.
Modeling of dispersion in
case of low located sources of pollution
At research of air pollution from low located sources (for example, chimneys at level of height of a building or exhaust gases of cars) it is necessary to consider influence of surrounding constructions. The considerable part of exhaust gases of cars can be late in deep "canyons" of streets. For the description of this process empirical laws (Yamartino and Wiegand 1986) have been found.
The polluting substances which are let out by low located chimney on a roof of a building, are picked up by air circulation alee buildings. The amplitude of this leeward circulation depends on height and width of a building, and also from speed of a wind. Hence, in that case basically the simplified methods of the description of dispersion of the polluting substances, the buildings based exclusively at height are unsuitable. Vertical and horizontal parameters of leeward circulation have been received as a result of aerodynamic researches (Hosker 1985) and can be applied in the diagnostic models based on stability of weight. After definition of area of a stream it can be used for calculation of carrying over and turbulent mixing of let out polluting substance. Whether it is possible to reach by means of dispersion modeling on Lagranzh on Euler.
More detailed researches - concerning, for example, casual emissions - can be spent only with use of models of not hydrostatic stream and dispersion, instead of a diagnostic method. As for this purpose the computer facilities of high capacity, as a rule, are required, before the beginning of construction of full statistical model it is recommended to apply the method of modeling of the worst possible situation described above.