78
..........
R.H. Charlier and Chr. P. De Melter
in which •
ca
= reference concentration
Ha
= effective transport velocity of bed-load particles
= reference level (= bed-load layer thickness)
Introduction ofeq. (32) and (34) in eq+ (33) yields "
qs
1
qt
[(F-l)(~-a/u)(a/h)]-+-I
(35)
The ratio u s / u may be identified as the ratio of the average transport velocity of
the bed-load and suspended load particles, which varies from about 0.4 for large,
steep bedforms in the lower flow regime to about 0.8 for fiat bed conditions in the
upper flow regime. Fig. 11 shows the ratio of the suspended load and the total
load as a function of the ratio of the bed-shear velocity and particle fall velocity
for different values of u s /u with n = 0+4, 13 = 1 and a/h=0.05. An empirical
relationship given by Laursen (1958) and data from Guy et aL (1966) are also
shown.
1+(
..............
~,°'tll
0.( l
02
°:I
10 -t
• =Ool
~,
.%., -~
III ......... ,.
1
I
•
[w
I
, !,l
. :o~' ,~-r~lllll
i i ; ito/Z,,¢-)" J
tllll
,
+ ~/:/Y
~'z
t! ,~L'~"~°"
11tll
!1'1!
"
i
t, ?+!o i.++i,o+ ,
lllll
'
'= ~f i i
o ~ >~.Ll+t++l .......
!, I U
10 °
~01
Fig. 11 "Ratio of suspended and total transport.
Van R~n (1984)
------ Laursea (1958)
• d~O : 190 Ym l
o ~so
2?0 pm
• d~o
280 yr'n
6 d~, o
450 pm
0 d~O
930 3Jr'~
t
measurements Guy et aI. (t953)
n :0,1-0,3m