Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
A numerical experiment on pollutant dispersion in a horizontally-homogeneous atmospheric boundary layer
Abstract A simplified turbulent closure model is proposed and utilized for simulation of the three dimensional dispersion of pollutant concentration. Since the present model is complex to an extent between the Level 2 and 3 models discussed in Mellor and Yamada (1974), it may be tentatively referred to as a “Level 2.5 model”. The Level 2.5 model is much simpler than the Level 3 model because only one transport equation for the turbulent energy is required to be solved, while seven transport equations are required for the Level 3 model when, for example, pollutant, wind, temperature and water vapor quantities are simulated. It is for this simplicity that the Level 2.5 model is proposed despite certain deficiencies in comparison with higher-level models. In the first part of the paper, the ability of the Level 2.5 model to simulate the diurnally varying planetary boundary layer of the “Wangara” experiment where previously the Level 3 model was utilized. The Level 2.5 model reproduced well the Level 3 model results except in the layer near the ground where the difference was greatest. In the second half of the paper a three-dimensional mass-conservation equation for a chemically inert pollutant is integrated numerically, with use of mean and turbulence fields from the numerical results of the first part. As expected, the results indicate large differences in the computed profiles of pollutant concentration between days and nights due to changes in stability. The values of the surface pollutant concentration are significantly reduced, especially during the nights when the effective stack height is 200 m.
A numerical experiment on pollutant dispersion in a horizontally-homogeneous atmospheric boundary layer
Abstract A simplified turbulent closure model is proposed and utilized for simulation of the three dimensional dispersion of pollutant concentration. Since the present model is complex to an extent between the Level 2 and 3 models discussed in Mellor and Yamada (1974), it may be tentatively referred to as a “Level 2.5 model”. The Level 2.5 model is much simpler than the Level 3 model because only one transport equation for the turbulent energy is required to be solved, while seven transport equations are required for the Level 3 model when, for example, pollutant, wind, temperature and water vapor quantities are simulated. It is for this simplicity that the Level 2.5 model is proposed despite certain deficiencies in comparison with higher-level models. In the first part of the paper, the ability of the Level 2.5 model to simulate the diurnally varying planetary boundary layer of the “Wangara” experiment where previously the Level 3 model was utilized. The Level 2.5 model reproduced well the Level 3 model results except in the layer near the ground where the difference was greatest. In the second half of the paper a three-dimensional mass-conservation equation for a chemically inert pollutant is integrated numerically, with use of mean and turbulence fields from the numerical results of the first part. As expected, the results indicate large differences in the computed profiles of pollutant concentration between days and nights due to changes in stability. The values of the surface pollutant concentration are significantly reduced, especially during the nights when the effective stack height is 200 m.
A numerical experiment on pollutant dispersion in a horizontally-homogeneous atmospheric boundary layer
Yamada, Tetsuji (Autor:in)
Atmospheric Environment ; 11 ; 1015-1024
04.03.1977
10 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
| British Library Conference Proceedings | 2012