Geoscience Reference
In-Depth Information
Yang formula
Yang (1973, 1984) related the bed-material load transport to the unit stream power
as follows:
N log US f
ω
U c S f
ω
log C t =
+
s
M
(3.106)
s
where C t is the sediment concentration in parts per million (ppm) by weight, U c is
determined using Eq. (3.29), and M and N are coefficients. For sand ( d
2 mm)
0.286 log ω
s d
ν
0.457 log U
ω s
M
=
5.435
0.409 log ω
s d
ν
0.314 log U
N
=
1.799
(3.107)
ω
s
and for gravel
(
2mm
<
d
<
10 mm
)
0.633 log ω
s d
ν
4.816 log U
ω
M
=
6.681
s
0.305 log ω
s d
ν
0.282 log U
ω
N
=
2.784
(3.108)
s
Ackers-White formula
The transport of coarse sediments, which are mainly in bed load, is attributed to the
stream power corresponding to the grain shear stress,
τ b U , while the transport of fine
sediments, which are mainly in suspended load, is related to the turbulence intensity
and in turn the total stream power,
τ b U . Based on this concept, Ackers and White
(1973) proposed a mobility factor of sediment transport:
1 n
U n
U
32 log
F gr
=
(3.109)
[
1
)
gd
]
1
/
2
(
/
)
10 h
d
s
and related the bed-material load to this mobility factor as follows:
U U
n
F gr
A c
1 m
C t h
d
G gr
=
=
(3.110)
γ
s
where C t
is an empirical coefficient, m
is an empirical exponent, n is the transition exponent, and A c may be interpreted as
the critical value of F gr for sediment incipient motion. Coefficients
is the sediment concentration by weight,
, A c , m , and n
3 , as listed
in Table 3.5, based on best-fit curves of laboratory data with sediment sizes greater
than 0.04 mm and Froude numbers less than 0.8.
2
1
/
were related to the dimensionless grain diameter D
=
d
[
1
)
g
]
s
 
Search WWH ::




Custom Search