66
...... R.H. Charlier and Chr. P.,,De Meyer
Van Rijn (1984) presented a simplified method based on the application of eq.
(17) to describe the concentration profile in combination with a modified
suspension number Z' defined as "
W~,m = (1 - C) Y w~
(A)
in which :
W~,m = particle fall velocity in a suspension
w+
= particle fall velocity in a clear fluid
c
= volumetric sediment concentration (-)
y
= coefficient (-)
Z' =Z+~F
(18)
u: ,ds°"12° prn q=O.1 rnZts =~ ktko
, ~,=~ q ~-,/+~
\.
++,\
-_0.o,
.=0.8
0,10
\
\
m
1245
0,0S
00
0.2
0.4._ 0.6
0.8
+,0 -- ~ O 0
~0
~
-~0
4o
•
C/C+
~
COHC~rI"2~": OH ¢ Ill
• .. ~xDcrlrn~n~s
--cornl~uted, inclt~ia 9 hin0tzrctd sa'L,ir~.
Fig. 8 - (a) Measured Concentration profiles (Winterwerp et al, 1989)
(b) Von Kannan coefficient as a fimction of concentration.
in which :
Z
=
suspension number
q~ =
correction factor representing hindered settling effects and turbulence
damping effects.
The W-factor can be determined as follows. First, the concentration profile is
computed numerically solving eq. (6) and applying eq. (A) to represent the fall
velocity w~,m and eqs. (10), (11), (13) to represent the sediment mixing
coefficient. Second, the concentration profile is computed from eqs+ (17) and
(18), applying a ~/ -factor that yields a concentration profile similar to that
obtained by the first (numerical) method.