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computing the fractional transport rate of non-uniformbed load. Based on the assump-
tion that the motion of fine particles is dominated by the lift force while the motion
of coarse particles is by the drag force, Misri
et al
. (1984) proposed a semi-theoretical
hiding-exposure correction factor. This correction factor was revised subsequently by
Samaga
et al
. (1986a) and Patel and Ranga Raju (1996). In the latest version published
by Patel and Ranga Raju, the bed-load function is shown in Fig. 3.16, in which the
dimensionless bed-load transport rate and the effective shear stress are
q
b
∗
k
bk
=
s
(3.77)
gd
k
p
bk
γ
(γ
/γ
−
1
)
s
τ
b
τ
=
ξ
(3.78)
eff
b
S
1
/
2
f
d
1
/
6
65
τ
b
=
γ
R
b
S
f
,
R
b
=
(
Un
/
3
/
2
,
n
=
where
)
/
24, and
ξ
b
is the hiding-exposure
correction factor for the effective shear stress determined by
τ
∗
k
)
−
0.75144
C
m
ξ
b
=
0.0713
(
C
s
(3.79)
τ
∗
k
=
τ
b
/
[
(γ
with
−
γ)
d
k
]
,
s
(τ
b
/τ
(τ
b
/τ
2
log
C
s
=−
0.1957
−
0.9571 log
)
−
0.1949
[
log
)
]
c
c
(τ
b
/τ
3
,
+
0.0644
[
log
)
]
c
Figure 3.16
Fractional bed-load function (Patel and Ranga Raju, 1996).
