2.1. Physical Parameters
15
FIGURE 2.1. Solute transport in a
dead-end pore.
fluid, we have
v = V' = qjn,
where q is the Darcy velocity and n the porosity.
Volumetrie Fraction
.....-hY-i"-+-,4...,d::;ead-end
pores
(2.1.26)
We have defined porosity n based on the REV of porous media in Equation
(2.1.1), which is, in fact, the volume fraction of the pore space in the REV.
Hence, the fraction of solid matrix can be written as (1 - n). Those pores,
which are not connected to other pores, will not take part in flow or mass
transport in groundwater, and are normally not treated as part of the pore
space. The porosity defined in this way is called the effective porosity, which
will be used throughout this book unless otherwise specified.
Some pores, though connected to others, are dead-end pores as shown in
Figure 2.1. The flow velocity inside them is extremely low and the fluid is
almost stagnant. In the study of solute transport, the effect of dead-end pores
must be taken into account. The pollutants inside these pores can only be
transported by molecular diffusion, and not by advection. Since molecular
diffusion is a slow process, removal of pollutants from these pores may take
a long time.
The saturated zone and unsaturated zone need to be treated separately
when we study the solute transport. In a saturated zone, the volume fraction
of fluid equals porosity n of the porous media, while in an unsaturated zone,
there exists a gas phase, as weIl as solid and liquid phases. The volumetrie
fraction of water
() = Volume of water in REV
w
Volume of REV
15
FIGURE 2.1. Solute transport in a
dead-end pore.
fluid, we have
v = V' = qjn,
where q is the Darcy velocity and n the porosity.
Volumetrie Fraction
.....-hY-i"-+-,4...,d::;ead-end
pores
(2.1.26)
We have defined porosity n based on the REV of porous media in Equation
(2.1.1), which is, in fact, the volume fraction of the pore space in the REV.
Hence, the fraction of solid matrix can be written as (1 - n). Those pores,
which are not connected to other pores, will not take part in flow or mass
transport in groundwater, and are normally not treated as part of the pore
space. The porosity defined in this way is called the effective porosity, which
will be used throughout this book unless otherwise specified.
Some pores, though connected to others, are dead-end pores as shown in
Figure 2.1. The flow velocity inside them is extremely low and the fluid is
almost stagnant. In the study of solute transport, the effect of dead-end pores
must be taken into account. The pollutants inside these pores can only be
transported by molecular diffusion, and not by advection. Since molecular
diffusion is a slow process, removal of pollutants from these pores may take
a long time.
The saturated zone and unsaturated zone need to be treated separately
when we study the solute transport. In a saturated zone, the volume fraction
of fluid equals porosity n of the porous media, while in an unsaturated zone,
there exists a gas phase, as weIl as solid and liquid phases. The volumetrie
fraction of water
() = Volume of water in REV
w
Volume of REV