FISICA AMBIENTALE 2
PARTICOLATO
Antonio Ballarin Denti
[email protected]
LE PARTICELLE
Volume fraction of aerosol particles in 4 quite different locations
Stages in the absorption of gaseous SO2 ina raindrop
Cattura di SO2 da parte di una goccia di pioggia
c (r > R, t = 0) = c∞
c (r→∞, t ) = c∞
c (R, t) = cs (t)=0
c (r, t = 0) = 0
r≤R
r = 0, t > 0
c (R, t) = cs
t>0
c (r, t→∞ ) = cs
r≤R
Cattura di SO2 da parte di una goccia di pioggia
Characteristic diffusion times in air and water for some drop sizes
Dg = 10-5 m2 s-1
R(m)
τair
τdrop
Da = 10-9 m2 s-1
10-3(1 mm)
10-4
10-5 (10 μm)
2.5 × 10-2
2.5 × 10-4
2.5 × 10-6
102
1
10-2
Fluxes at the interface air-water drop.
The interface may be considered flat at x = 0
Cattura di SO2 da parte di una goccia di pioggia
Derivation of Stokes’law
Fluid is flowing from bottom to top with a non-slip condition
at the surface. On the left one finds the general coordinate
system, on the right the forces at the surface of the sphere.
The drag is determinated by the components of the pressure
force and tangential force in the direction of the flow.
LE PARTICELLE
Attrito su una singola particella