The present research introduces a technique to determine pollution source locations in urban environments -when the pollutant concentration field is known- through the use of reversed time marching method (RTMM). The method depends primarily on the solution of the scalar transport equation with time integration in the negative direction. This leads to reversing the velocity field and also the diffusion term. The study demonstrates how to use the inverse CFD model with the reversed time marching method to identify pollution sources in urban environments. In order to examine the accuracy of RTMM in identifying pollution sources in urban areas, two examples were given. In the first one, a simple laminar flow was considered and a pollutant source was emitted for variable wind conditions. In the second example, the wind flow around a single building was investigated for two different source locations. In all cases, steady state numerical simulations were carried out at first in order to estimate the wind flow fields. With the steady-state airflow patterns, direct CFD modeling (forward-time simulation) was used to calculate pollutant concentration distributions for step-function sources. In the last stage, the scalar transport equation was solved again but with the reversed flow field and the negative diffusion term. By using peak concentration, one could identify the pollution source location. Results of the study demonstrated that the RTMM can identify pollution sources locations in urban areas with a satisfied accuracy. However, more efforts are needed in order to decrease the wide spread of the concentration fields around the source location and facilitates the source location identification.
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KEYWORDS: Reverse simulation; Reversed time marching method; Outdoor environments; CFD
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