Environmental Engineering Reference
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Fig. 2.3 Comparison of LES results with the RANS model (for different subdomains A-D) for
the concentration of the 64% Emission Surface/Grid-Cell Surface scenario
only transported and dissipated. This is likely to be due to the lack of resolution in
advection schemes since only a few grid points are considered.
From the beginning, we assumed that the LES represented true atmospheric
motion due to its high resolution and accuracy in simulating atmospheric flow and
dispersion. Within the LES domain we introduce 10 virtual measuring locations
(Fig. 2.4) to investigate how the use of the emission variance parameterization will
improve 3D RANS model results when compared with instantaneous measurements
collected at 10 points (1-10) in Fig. 2.4.
Figure 2.5 shows the time evolution of concentration sampled at 12.5m for the
two emission patterns at 10 locations. The data are instantaneous concentration
values produced by the LES with a 5 minute frequency. The thick black lines are
the concentrations obtained from the 3D model whereas the shading is correspond
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