Geoscience Reference
In-Depth Information
Figure 3.21
Relation of
C
∗
and
U
3
/(
gR
ω
s
)
(Zhang, 1961).
by the
C
k
U
3
curve calibrated using multiple-sized sediment data. How-
ever, Wu and Li's (1992) method does not explicitly consider the hiding and exposure
effect among non-uniform sediment particles.
∼
/(
gR
ω
sk
)
Wu et al. formula
Based on Bagnold's (1966) stream power concept, Wu
et al
. (2000b) related the
suspended-load transport rate to the rate of energy available in the alluvial system and
to the resistance to sediment suspension. The former was expressed as
τ
U
, and the
latter was accounted for by the settling velocity
ω
s
and the critical shear stress
τ
c
. Here,
τ
is the shear stress on the wetted perimeter of the cross-section:
τ
=
γ
RS
f
. Through
/ω
s
was derived. By
using the laboratory data of non-uniform suspended load measured by Samaga
et al
.
(1986b) and two sets of field data in the Yampa River and the Yellow River, the
relation between the fractional suspended-load transport rate
q
s
∗
k
and the parameter
(τ/τ
ck
−
(τ/τ
c
−
)
dimensional analysis, the independent parameter
1
U
1
)
U
/ω
sk
was established. It is shown in Fig. 3.22 and expressed as
0.0000262
τ
1
U
ω
sk
1.74
=
τ
ck
−
(3.102)
sk
p
bk
gd
k
]
where
, with
q
s
∗
k
being the suspended-load trans-
port rate by volume per unit time and width (m
2
s
−
1
); and
sk
=
q
s
∗
k
/
[
(γ
/γ
−
1
)
s
τ
ck
is determined using
Eq. (3.45), which takes into account the hiding and exposure effect in non-uniform
sediment transport. The sediment settling velocity
ω
sk
is calculated using the Zhang
formula (3.12).
