1. Computational Fluid Dynamics ( CFD ) Modeling of Building-scale Dispersion Shuming Du September 12, 2002 Air Resources Board California Environmental Protection Agency Working Draft - Do Not Cite or Quote

2. What are CFD Models? l CFD models numerically solve basic equations of fluid dynamics, similar to what MM5 and RAMS do for meso- and regional scales l CFD models focus on detail features in a small scale setting, e.g., flow around individual buildings l A dispersion model can be built into CFD model or stand-alone  stand-alone is used in ozone/PM modeling, i.e., generate flow field first and then use it to drive dispersion model Working Draft - Do Not Cite or Quote

3. Motivation: Why CFD Models? l Sometimes we need to estimate concentrations from sources just across the street l Regulatory models are not capable of simulating the extremely complex wind fields and dispersion of pollutants in these conditions Working Draft - Do Not Cite or Quote Receptor

4. GASFLOW l Many commercial and public-domain models are available, GASFLOW is chosen because:  Available to the public  Can be used in both outdoor and indoor environments  Option to use particle model to calculate dispersion therefore avoiding problems associated with K-theory Working Draft - Do Not Cite or Quote

5. Preliminary Results l Model has not been tested l Some features are not consistent with what we know l Dispersion model is not correct, still needs improvement l The purpose of the following plots is merely to show what a CFD model can do Working Draft - Do Not Cite or Quote

6. Preliminary Results l Two one-story 15 m x 6 m x 5 m buildings, 16 m apart l Two source locations Working Draft - Do Not Cite or Quote Wind Source 2 Source 1

7. Preliminary Results l Modeling domain: side-view Working Draft - Do Not Cite or Quote

8. Preliminary Results l Modeling domain: top-view Working Draft - Do Not Cite or Quote

9. Preliminary Results l Wind field: side-view Working Draft - Do Not Cite or Quote

10. Preliminary Results l Wind field: side view Working Draft - Do Not Cite or Quote

11. Preliminary Results l Modeling domain: top-view (at z = 25 cm) Working Draft - Do Not Cite or Quote

12. Preliminary Results l Modeling domain: top-view (at z = 425 cm) Working Draft - Do Not Cite or Quote

13. Preliminary Results l Modeling domain: top-view (at z = 745 cm) Working Draft - Do Not Cite or Quote

14. Preliminary Results l Diffusion from source 1 (top view) Working Draft - Do Not Cite or Quote

15. Preliminary Results l Diffusion from source 1 (side view) Working Draft - Do Not Cite or Quote

16. Preliminary Results l Diffusion from source 1 (angled view) Working Draft - Do Not Cite or Quote

17. Preliminary Results l Diffusion from source 2 (top view) Working Draft - Do Not Cite or Quote

18. Preliminary Results l Diffusion from source 2 (side view) Working Draft - Do Not Cite or Quote

19. Preliminary Results l Diffusion from source 2 (angled view) Working Draft - Do Not Cite or Quote

20. Future Work l Modify the model to address the problems revealed in the preliminary work l Correct the dispersion algorithm to reflect the latest development of Lagrangian particle modeling l Test the model against EPA wind tunnel experiment and real-world data collected at Logan Memorial Junior High School and at CE-CERT, UC Riverside Working Draft - Do Not Cite or Quote

21. Future Work (continued) l This work may eventually enhance our modeling capability in dealing with dispersion at building scale, for example, estimating concentrations caused by chrome plating facilities in Barrio Logan Working Draft - Do Not Cite or Quote