Aeration Mechanisms - Soil Physics - Lecture Slides, Slides of Soil Physics

Download Aeration Mechanisms - Soil Physics - Lecture Slides and more Slides Soil Physics in PDF only on Docsity!

Outline

• Announcements
• Aeration
• Permeability
• Relative permeability
• Air permeability

Aeration

Advection

Darcy’s law is about advection (or mass flow):

dx

d

Q Ks

ψ

Mass moved (flux density)

Proportionality coefficient

Potential gradient

Now replace the water with molasses

(keep the same soil, same potential gradient)

dx

d

Q Ks

ψ

Same flux? Same proportionality coefficient?

Same potential gradient

K s has 2 parts:

• Soil properties
• Fluid properties docsity.com

What’s with the L 2?

Permeability k L^2

dx

g d

Q k

ψ

η

ρ

The actual length L that is squared for a soil’s permeability is quite small.

It is usually interpreted as the soil’s effective pore diameter.

Back to water, molasses, etc.

dx

g d

Q k

ψ

η

ρ

Soil permeability fluidity

The soil’s permeability does not depend on the fluid’s properties.

So permeability can also describe the flow of air

Relative permeability

k r

0

1

0 Sw 1 1 Sa 0

Petroleum engineers, and some geologists, use these “relperm” plots

air entry value

Air permeability k a

0 Sw 1

k a

0

1

1 Sa 0

h

0

No air flow until soil has dried to the air entry value.

This is like θr

for hydraulic conductivity:

K (θr) = 0

docsity.com