Geoscience Reference
In-Depth Information
(e)
when the pore-filling fluid is non-Newtonian (i.e. when the shear stress is a nonlinear
function of the rate of strain);
(f)
when the porous matrix is non-elastic in the sense of Hooke's law. Note: porous matrix
refers to the bulk solid, but not to the material out of which the grains are made.
8.18
Multiple choice. Indicate which of the following statements are correct. A large, geological forma-
tion consisting of a uniform, partly saturated, anisotropic non-swelling porous sand has a hydraulic
conductivity, that may be characterized as follows:
(a)
k
=
k
(
θ,
x
,
y
,
z
) and independent of direction;
k
ij
=
k
ij
(
x
,
y
,
z
) consisting of 2
2
(b)
=
4 components;
k
ij
=
k
ij
(
x
,
y
,
z
) consisting generally of 3 components regardless of the orientation of the
axes system;
(c)
(d)
k
ij
=
k
ij
(
θ
) in which the form of the functional relationship with
θ
does not depend on
x
,
y
,
z
;
(e)
it is usually assumed that
k
ij
=
k
ji
.
8.19
Multiple choice. Indicate which of the following statements are correct. The hydraulic conductivity
of a partly saturated clayey soil (i.e., the capillary conductivity):
(a)
is sharply reduced in the initial stages of reduction of water content;
(b)
as a function of water pressure usually displays marked hysteresis;
(c)
increases with increasing hydraulic gradient;
(d)
is temperature dependent;
(e)
may depend on the type of salt that is in solution in the water.
8.20
Multiple choice. Indicate which of the following statements are correct. It is known that Darcy's
law fails to describe the flow in a porous medium when the Reynolds number increases into the
range between 1 to 10 and up. This initial deviation is the result of:
(a)
the presence of electrically charged clay particles;
(b)
the fact that water is non-Newtonian at low velocities;
(c)
the effect of inertia (i.e. convective acceleration of fluid particles);
(d)
the onset of local turbulence;
(e)
flow instabilities in the pore necks so that the flow develops local separation eddies;
(f)
the fact that the flow is non-laminar but still creeping.
(8.21)
Multiple choice. Indicate which of the following statements are correct. Assume that the flow of
a wetting fluid in an elastic porous material can be described by the first of Equations (8.82). A
simplified form of that equation, namely Laplace's equation,
0, is valid to describe flow
in a uniform (prior to flow), isotropic, fully saturated porous material whenever:
(a)
∇
2
p
w
=
the flow is steady, the fluid compressible and the porous matrix compressible;
(b)
the flow is unsteady, the fluid incompressible and the porous matrix incompressible;
(c)
the flow is steady, the fluid compressible and the porous matrix incompressible;
(d)
the flow is unsteady, the fluid compressible and the porous matrix incompressible;
(e)
the flow is steady, the fluid is incompressible and the porous matrix compressible;
(f)
the flow is steady, the fluid and the porous matrix are both incompressible.
