Atmospheric Dispersion with a Large-Eddy Simulation
257
a low source (Figure 9.6b) in the CBL. Points connected with the blue line are data
obtained from Willis and Deardorff laboratory dispersion experiments; the red line
is obtained from the present Eulerian model.
9.3.7 CONCLUSIONS FOR THE EULERIAN EXPERIMENTS
Results obtained from the simulations indicate that our model can successfully simulate the Eulerian dispersion of passive contaminants in high-resolution turbulent
fi elds provided by LES. The Eulerian approach to studying pollutant dispersion and,
particularly, the developed scheme based on a splitting technique to numerically
solve the conservation equation, produce good results. In general, the main problem in dealing with this kind of scheme is the numerical discretization of advective
terms, which may present many complications. The spline technique used to solve
these terms has been preferred, as it can be easily adapted to a domain with irregular
grid-spacing (Long and Pepper, 1981). Since our LES code has been accurately tested
(Moeng, 1984), we have only tested the numerical scheme and its matching with the
LES model. We then simulated pollutant dispersion from an elevated and low continuous point source in a CBL and from an elevated point source in a shear-driven
boundary layer. Our dispersion experiment results are in good agreement with the
classical ones found in the literature. The nontrivial characteristics of dispersion are
adequately captured, and the crosswind-integrated concentration distribution closely
resembles the well-established numerical and laboratory experiments found in the literature. Results confi rm that the LES constitutes an alternative to fi eld experiments:
it can provide databases of dispersion data on which a wide range of dispersion models can be developed and tested, in view of their use in air quality applications.
2.8
2.4
2.0
1.6
1.2
X *
z/h
0.8
0.4
0.0
3.75
2.75 3.25
2.25
2.00
1.50
1.00
1.25
0.750
0.250
0.500
0.500
0.750
1.75
3.50
3.00
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2.50
FIGURE 9.5 Isopleths of adimensional crosswind-integrated concentration averaged over
last 3000 time steps.
© 2010 by Taylor and Francis Group, LLC
257
a low source (Figure 9.6b) in the CBL. Points connected with the blue line are data
obtained from Willis and Deardorff laboratory dispersion experiments; the red line
is obtained from the present Eulerian model.
9.3.7 CONCLUSIONS FOR THE EULERIAN EXPERIMENTS
Results obtained from the simulations indicate that our model can successfully simulate the Eulerian dispersion of passive contaminants in high-resolution turbulent
fi elds provided by LES. The Eulerian approach to studying pollutant dispersion and,
particularly, the developed scheme based on a splitting technique to numerically
solve the conservation equation, produce good results. In general, the main problem in dealing with this kind of scheme is the numerical discretization of advective
terms, which may present many complications. The spline technique used to solve
these terms has been preferred, as it can be easily adapted to a domain with irregular
grid-spacing (Long and Pepper, 1981). Since our LES code has been accurately tested
(Moeng, 1984), we have only tested the numerical scheme and its matching with the
LES model. We then simulated pollutant dispersion from an elevated and low continuous point source in a CBL and from an elevated point source in a shear-driven
boundary layer. Our dispersion experiment results are in good agreement with the
classical ones found in the literature. The nontrivial characteristics of dispersion are
adequately captured, and the crosswind-integrated concentration distribution closely
resembles the well-established numerical and laboratory experiments found in the literature. Results confi rm that the LES constitutes an alternative to fi eld experiments:
it can provide databases of dispersion data on which a wide range of dispersion models can be developed and tested, in view of their use in air quality applications.
2.8
2.4
2.0
1.6
1.2
X *
z/h
0.8
0.4
0.0
3.75
2.75 3.25
2.25
2.00
1.50
1.00
1.25
0.750
0.250
0.500
0.500
0.750
1.75
3.50
3.00
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2.50
FIGURE 9.5 Isopleths of adimensional crosswind-integrated concentration averaged over
last 3000 time steps.
© 2010 by Taylor and Francis Group, LLC