Chemical reactions at street scale using a Lagrangian particle dispersion model (LPDM)

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Lorraine Blake
5 years ago
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la Ferme 92100 Boulogne Billancourt France

1 ARIA Technologies Chemical reactions at street scale using a Lagrangian particle dispersion model (LPDM) H. Kaplan, C. Orly, J. Moussafir, O. Oldrini, F. Mahe and A. Albergel ARIA Technologies SA 8-10, rue de la Ferme Boulogne Billancourt France Telephone: +33 (0) Fax: +33 (0) info@aria.fr

2 CONTEXT : Urban air quality x emissions Boiler Domestic heat District Traffic Are 2 concentrations compliant with UE Standards? ARIA Technologies 2

3 Goals of the study Chemical reaction formulation for LPDM at street level. Are the segregation terms significant? Sensitivity to the / 2 ratio in the emission source. Sensitivity to the city level background. What are the relevant reactions at street scale applied to traffic pollution for operational use? ARIA Technologies 3

4 Study case Domain and Air Quality measurements Hausmann OPERA 1 km ARIA Technologies 4

5 Model formulation Chemical reactions The model describes emission of x from traffic inside a constant background of ozone, BO 3 Each particle released from the source carries an initial mass of (m ), 2 (m 2 ) and a deficit from the Ozone background (mdef O3 ) [Alessandrini et. al. (2009) see also H14-188] + O O 2 (k=0.31) [1/(ppm.s)] 2 +O 2 + hν + O 3 (J=0.0145e 0.4/cosQ ) [1/s] ARIA Technologies 5

6 Model formulation dm dt The rate of change of particle s content dm dt 2 dm Concentration defo dt 3 k( BO m ) 3 C mdefo3 Summation in cell divided by the cell volume gives the average reaction rate equation d C dt k C d C O 3 C 2 dt J k C 2 C ( B O C ) 3 defo3 J C 2 Jm 2 ARIA Technologies 6

7 Model formulation Traffic induced turbulence The moving vehicle induces a turbulence which effect the pollutant dispersion near the source. This turbulence is modeled as an injected TKE with emission rate which should be modeled or measured. Q TKE Simple Model N - the number of vehicles per second Q the X emission rate The emitted amount of X by a single vehicle ~ 0.2g/s V - the average velocity of the vehicle (~10m/s) 2 The amount of TKE per vehicle ~ ( V ) 0.1 Q TKE N( V) 5 KQ ARIA Technologies 7 2 N Q

8 The segregation term Definition The Conditional Concentration The segregation term can be considered as a correction in the reaction equation by the conditional concentration dm dt A+B C da/dt=db/dt=kab d<a>/dt=d<b>/dt=k<ab>=k(<a><b> + <A B > ) dm dt 2 dm dt defo 3 C k( BO m ) 3 C mdefo3 Jm 2 ARIA Technologies 8

9 The segregation term The conditional concentration The conditional concentration is the average concentration for particles along their trajectories The time evolution of conditional concentration is given by: C C dc C C dt T The mixing time Tmix is proportional to the Lagrangian time scale (Tmix =0.6 TL) mix Including the segregation term has a negligible influence on the results at street scale ARIA Technologies 9

10 Model input data Traffic emission data ( x ) At 3:00 At 15:00 ARIA Technologies 10

Model input data Meteorological (MM5) and O 3 data Date : 25.02.

11 Model input data Meteorological (MM5) and O 3 data Date : Wind speed z= 54m (Umax=6m/s) Wind direction Mixing Height Hmax=500m Ozone Background Eiffel Tower (~300m) [O 3 max]= 60µg/m 3 ARIA Technologies 11

12 Results Reference case / X ratio = 0.75 Turbulence parameter K = 0.5 Total X Concentration HAUSSMANN OPERA (red: measured ; green calculated) ARIA Technologies 12

13 Results 2 HAUSSMANN HAUSSMANN OPERA OPERA (red: measured ; green calculated) ARIA Technologies 13

14 Results 2 BACKGROUND INFLUENCE Without 2 background HAUSSMANN With 2 background HAUSSMANN OPERA OPERA (red: measured ; green calculated) ARIA Technologies 14

Results 2 predicted concentration 24.07.2012 4.09.

15 Results 2 predicted concentration HAUSSMANN HAUSSMANN OPERA OPERA ARIA Technologies (red: measured ; green calculated) 15

16 Sensitivity study Ref case : / X =0.75 K=0.5 B O3 =44 At 15:00 2 ARIA Technologies 16

17 Sensitivity Analysis Ref : / X =0.75 K=0.5 B O3 =44 CALCULATED MEASURED H O H O Concentrations at 15:00 2 (51) 76 (75) (30) 55 /X=0.9 K=0.25 BO3=88 H O H O H O (42) 66 (65) 90 (80) 105 (63) 89 (90) g / m Numbers in parenthetic are without 2 background ARIA Technologies 17

18 The generic reaction set (GRS) ROP in GRS The GRS equations describes reactions of and 2 with radical products (RP). RP 2 RP are result of photo-dissociation of reactive organic compounds (ROP) ROP h RP ROP The time-scale of RP production from photo-dissociation of ROP is much larger than the transport time over domain of 1x1 Km ROP emitted in the area will not affect the results If RP are known in the background, the whole set of the GRS should be solved and the result depends on the amount of RP background concentration. ARIA Technologies 18

19 CONCLUSION The current LPDM model was extended to include chemical reaction and self induced turbulence The segregation term is not important at street scale but should be included for large plume whose magnitude is much smaller than the turbulence scale. / X =0.75 for Paris area and is not a free parameter of the model It is important to well assess 2 background when modeling an isolated district The whole set of GRS equation should be solved only in case that there is a large background concentration of RP ARIA Technologies 19

20 Next step : 2 for «AirCity» Project Compute and forecast meteorological and air quality parameter within a 3m resolution Need of HPC : Ex Paris at 3M resolution 360 CPU ARIA Technologies 20

21 Thank you for your attention! ARIA Technologies 21

22 The generic reaction set (GRS) ROP h RP 2 2 O h 3 RP ROP O 2 3 ROP- Reactive organic products RP- Radical Products SGN- Stable gaseous nitrogen products RP RP 2 2 SGN SNGN SNGN- Stable nongaseous nitrogen products ARIA Technologies 22

Christophe DUCHENNE 1, Patrick ARMAND 1, Maxime NIBART 2, Virginie HERGAULT 3. Harmo 17 Budapest (Hungary) 9-12 May 2016

Validation of a LPDM against the CUTE experiments of the COST ES1006 Action Comparison of the results obtained with the diagnostic and RANS versions of the flow model Christophe DUCHENNE 1, Patrick ARMAND