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TREATMENT FOR LAGRANGIAN TRANSPORT AND DIFFUSION OF SUBGRID PLUMES IN A EULERIAN GRID FRAMEWORK
Citation:
Godowitch, J., J.K.S. Ching, AND N. Gillani. TREATMENT FOR LAGRANGIAN TRANSPORT AND DIFFUSION OF SUBGRID PLUMES IN A EULERIAN GRID FRAMEWORK. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-95/061 (NTIS PB95218814).
Description:
Since Eulerian grid models cannot explicitly treat processes existing on spatial scales smaller than the grid cell size, it is imperative to be able to develop innovative approaches to simulate relevant subgrid scale features within the modeling grid framework. otable class of subgrid scale features consists of major elevated point source plumes, which contain significant amounts of NOx and SOx emissions. owever, the methodology for treating such plumes in most regional and urban air quality grid models is to instantaneously mix the pollutant emissions into an entire grid cell volume. his approach neglects the subgrid scale treatment of plume transport and dispersion, which also strongly impact plume chemistry. lthough there is a general trend in grid modeling toward finer grid cell sizes and nested grid capabilities, a power plant plume will remain a subgrid scale feature both physically and chemically for some period. he next generation of comprehensive air quality grid models must be capable of treating major point source plumes in a realistic manner in order to provide greater certainty and improved performance from model simulations. esearch and development effort is underway to deal with subgrid scale plumes by the design and incorporation of a plume-in-gr4-d approach in the EPA Models-3 system. he intent of this paper is to highlight the important aspects and methods being considered in this plume-in grid effort. he principal algorithms under development include a plume dynamics processor designed to provide plume location and size (i.e., horizontal and vertical dimensions) information and a Lagrangian reactive plume module (LRPM). escription is provided of processes and approaches included in the plume dynamics processor with selected preliminary results, and the notable features of the LRPM, which will be embedded in a nested grid model, are highlighted.