Geoscience Reference
In-Depth Information
being the correction coefficient defined in Eq. (3.31).
X
is the characteristic grain size
of bed material, defined as
X
=
0.77
s
if
/δ >
1.8 and
X
=
1.39
δ
if
/δ
≤
1.8,
s
s
U
∗
with
δ
being the laminar sublayer thickness (
=
11.6
ν/
).
Parker et al. formula
Based on the equal mobility concept, Parker
et al
. (1982) developed a gravel transport
function, as shown in Fig. 3.15, in which the dimensionless bed-load transport rate
W
k
is defined in Eq. (3.26) and the dimensionless shear stress
θ
k
is
hS
f
θ
k
=
(3.72)
d
k
τ
rk
(ρ
/ρ
−
1
)
s
τ
rk
=
where
0.0875
d
50
/
d
k
, with
d
50
being the subpavement size.
Figure 3.15
Gravel transport function of Parker
et al
. (1982).
Since all grain sizes are assumed to have approximately equal mobility, only one
grain size, the subpavement size
d
50
, is used to characterize the bed-load transport
rate as
0.0025 exp
2
[
14.2
(θ
−
1
)
−
9.28
(θ
−
1
)
]
0.95
<θ
<
1.65
50
50
50
W
k
=
4.5
11.2
(
1
−
0.822
/θ
)
θ
≥
1.65
50
50
(3.73)
