A New Algorithm to Solve Condensation/Evaporation Growth and Coagulation of Nanoparticles

1. A New Algorithm to Solve Condensation/Evaporation Growth and Coagulation of Nanoparticles Marion Devilliers1,2, Christian Seigneur2, Edouard Debry1, Karine Sartelet2 1National Institute of IndustrialEnvironment and Risk (INERIS), Verneuil en Halatte, France 2 Atmospheric EnvironnementCenter (CEREA), Joint Laboratory École des PontsParisTech/EDF R&D, Université Paris-Est, France European Geosciences UnionGeneral Assembly 2011 Vienna | Austria | 05 April 2011

2. Nanoparticles : a health concern • Definition : at least one of the dimensions of the particle is less than 100 nm • Potential adverse effects on human health • Multiple sources : • indoor air (domestic activities) • outdoor air (road traffic, ...)

3. Objectives of thisstudy • To be accurate with both number (important for nanoparticles) and mass (important for fine and coarse particles) • To correctly account for phenomena specific to nanoparticles such as Kelvin effect, van der Waals forces, electric forces for charged particles, and fractal aspect → development of an aerosol model suitable for both indoor and outdoor applications

4. The sectional approach • Development of a 0D model with particle size distribution discretized in N sections • Each section is characterized by a representative mean diameter, a number concentration and/or a mass concentration of particles • Hypotheses are: • temperature and particle density are constant • all particles have the same composition • particles are spherical

5. Initial distribution : regional pollution numberdistribution volume distribution

6. Initial distribution : diesel vehicles number distribution volume distribution

7. Condensation/Evaporation The volume variation at each time step for the section i is calculated using the following formula: with the Kelvin effect calculated as follows: and the partial gas pressure being updated at every time step because of mass conservation

8. Redistribution of the particles • To keep the representative diameter in the section, particles which are too large or too small are moved to the next or the previous section • To redistribute particles among sections, different schemes have been tested and compared

9. Standard redistribution schemes Euler-Mass: Euler-Number:

10. Advanced redistribution schemes • Moving-Diameter redistribution when diameter changes section (based on Jacobson scheme) • Full-Moving no redistribution, cannot be used in 3D but here as the reference (with 500 sections)

11. New schemes • Euler-Hybrid number redistribution for nanoparticles, mass redistribution for fine and coarse particles • Euler-Couple redistribution conserving both mass and number

12. Results : regional pollution Moving-Diameter and Euler-Hybrid show the best results

13. Results : diesel vehicles • Moving-Diameter • shows the best results • Euler-Hybrid • isbetterthan the • other Euler • schemes

14. Performance statistics Comparing to our reference using the formula (for the number) :

15. Coagulation Coagulation has been added to the model that simulate c/e with the Euler-Hybridscheme (using a splitting method)

16. Future work • Comparison of different coagulation kernels: • integrated over the section • based on representative diameter • Van der Waals forces will be taken into account for coagulation • A new other scheme:Euler - Irregular using a finer discretization for nanoparticles

17. Thank you for your attention