Geology Reference
In-Depth Information
Figure 2.
Mass Balance Diagram.
(
q
out
-
q
in
) = Change in storage
Now let us consider the flow along y-axis of the REV.
Influx to the elemental volume through the face,
X
Z
= (
q
y
)
in
Flux out = (
q
y
)
out
Volumetric outflow rate - Volumetric inflow rate
=[(
q
y
)
out
- (
q
y
)
in
] ×
X
Z
[(
q
)
(
q
)
]
.
X
Y
Z
y
out
y
in
Or
=
So change in flow rate along y-axis is given as
Y
-
-
q
y
=
' ×
X
Y
Z
(6)
Similarly change in flow rate along x-axis and z-axis is given as:
-
-
q
x
x
=
' ×
X
Y
Z
(7)
-
-
q
z
and
=
'
×
X
Y
Z
(8)
Now the
total change in flow rate = change in storage
We can allow the possibility of source or sink of water within an elemental
volume. The volumetric elemental volume is expressed as
R
X
Y
Z
, i.e.,
