Lattice Gas Wind Field Model

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The 19 th IASTED International Conference on Modelling and Simulation 2008 Quebec City, Quebec, Canada

Lattice Gas Simulation of Wind Fields in the Mexico City Metropolitan Area. A. Salcido, A.T. Celada, T. Castro

Instituto de Investigaciones Eléctricas, México

May, 2008

Motivation • Knowledge of the wind field is necessary for the modeling of transport and dispersion of pollutants.

• There are few information about the wind field in the Mexico City Metropolitan Area (MCMA).

In order to contribute to modelling of transport and dispersion of pollutants in the MCMA, we present a square lattice gas technique to define a 2D wind field diagnostic model to simulate the wind field in MCMA.

Lattice Gas Wind Field Model (LGWFM) Nx x Ny sites 3

2

4

8

6

5

1

0

7

Particle speeds 0

Æ Direction 8

1

Æ Directions 0, 2, 4, 6

21/2

Æ Directions 1, 3, 5, 7

Exclusion principle

Equilibrium distribution function

Mass, momentum and energy conservation

nα =

1 1 + e (ε α − μ ) / kT

Lattice Gas Wind Field Model (LGWFM)

1) Reproduction of laminar and turbulent situations such as Couette 2D plane flow.

2) Reproduction the quasi-logarithmic wind velocity vertical profile.

3) Application of LGWFM to simulate the steady state wind field in the Mexico City Metropolitan Area, for daytime and nighttime conditions

Couette Laminar Flow and Logarithmic Wind Velocity Profile 207 x 207 sites U = 0.1, 0.3, 0.5, 0.7 and 0.9

u* ⎡ ⎛ y ⎞ y ⎞⎤ ⎛ u(y) = ⎢ln⎜⎜ ⎟⎟ − ΨM ⎜ ⎟⎥ k ⎣ ⎝ yo ⎠ ⎝ L ⎠⎦ ⎡ y +1 ⎤ ΨM = a ( y − yo) ln ⎢ ⎥ ⎣ b ( y − 1) ⎦ y0 = 10.5 a = 0.2 b = 1.016 u*/k = 0.3

Lattice Gas Wind Field Model (LGWFM) to simulate wind fields in the MCMA

Laticce: 396 x 324 sites Spatial resolution: 180 m July 31 and August 26, 1994 9h

15 h

21 h

Lattice Gas Wind Field Model (LGWFM) to simulate wind fields in the MCMA RAMA

Date: 07/31/94

Local Time: 09:00 Measured

Station

WSP (m/s)

Estimated WDR (°N)

WSP (m/s)

WDR (°N)

IZTACALA

1.00

353

0.95

355

TEXCOCO

1.92

351

1.97

350

UNAM

0.97

5

1.00

3

IZTAPALAPA

0.71

4

0.78

0

TLANEPANTLA

----

----

1.55

313

SN. AGUSTIN

1.70

339

2.88

30

ACATLAN

1.21

300

0.88

305

TACUBA

----

----

0.38

297

HANGARES

1.70

324

2.53

24

C. ESTRELLA

1.21

2

1.08

338

PLATEROS

1.16

352

0.97

21

July 31, 1994,9 hr

July 31, 1994 15 hr

Date: 07/31/94

Local Time: 15:00 Measured

Station

Estimated

WSP (m/s)

WDR (°N)

WSP (m/s)

WDR (°N)

IZTACALA

2.50

354

2. 53

354

TEXCOCO

2.51

339

2.55

340

UNAM

1.33

8

1.34

8

IZTAPALAPA

2.23

47

2.30

47

TLANEPANTLA

----

----

4.13

318

SN. AGUSTIN

2.59

347

4.40

25

ACATLAN

3.53

32

2.19

334

TACUBA

----

----

2.16

326

HANGARES

4.10

15

3.30

14

C. ESTRELLA

2.28

26

1.79

348

PLATEROS

2.37

352

1.24

31

July 31, 1994 21 hr

Date: 07/31/94

Local Time: 21:00 Measured

Estimated

Station

WSP (m/s)

WDR (°N)

WSP (m/s)

WDR (°N)

IZTACALA

1.24

356

1.30

356

TEXCOCO

1.35

355

1.36

355

UNAM

0.45

25

0.49

24

IZTAPALAPA

1.79

71

1.83

70

TLANEPANTLA

----

----

4.13

318

SN. AGUSTIN

2.55

6

2.34

33

ACATLAN

3.40

200

1.52

170

TACUBA

----

----

1.23

153

HANGARES

2.41

216

2.00

40

C. ESTRELLA

1.88

341

0.43

9

PLATEROS

2.41

311

1.00

45

CONCLUSIONS • It is used a lattice gas techniques as an alternative approach to the wind field diagnostic problem, in 2D.

• The computer simulations to test the model showed off that it is capable to reproduce steady and non steady laminar and turbulent well known flow situations. In particular, it was capable to reproduce the typical surface layer quasi-logarithmic wind profile.

• Although the model is still in the validation and calibration phase, it was possible to estimate the wind field of the Mexico City Metropolitan Area with a reasonable agreement with the wind data measured at the meteorological stations of the automatic monitoring network of Mexico City.

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