Environmental Engineering Reference
In-Depth Information
w s
u
Vh
w s
L A =
exp( f )
(5.129)
L A
h =
w s
u
V
w s
exp( f )
(5.130)
w s
u
a i +
i 1
4
b i u
V
f
=
(5.131)
i
=
1
where:
c e =
concentration of suspended load in equilibrium condition
c
=
concentration of suspended load at distance x
c 0 =
concentration of suspended load at distance x
=
0
T A =
adaptation time (s)
L A =
adaptation length (m)
x
=
length coordinate (m)
w s =
fall velocity (m/s)
u =
shear velocity (m/s)
V
=
mean velocity (m/s)
h
=
water depth (m)
a i , b i =
constants
The adaptation length ( L A ) and adaptation time ( T A ) are constant for
uniform flow and are defined as the interval (both in length and in time)
required for the mean actual concentration to approach the mean equi-
librium concentration. The adaptation length and the adaptation time
represent respectively the length scale and the time scale (Ribberink,
1986).
To compute the adaptation time ( T A ) and adaptation length ( L A ), the
constants a i and b i are required. Galappatti (1983) used suspension param-
eters for natural channels and computed these constants for different ratios
of z/h 0 . The constants for T A and L A for z/h 0 =
0.01, 0.02 and 0.05
are given in Table 5.9. In steady and uniform flow, the adaptation length
( L A ) and adaptation time ( T A ) are constant and have straight characteris-
tics in the x - t plane. In gradually varied flow the water depth and velocity
change in each length step. Therefore L A and T A are not constant along
the canal. Furthermore, the magnitude of
decreases exponentially
with L A and T A . They are defined as the interval (both in length and time)
required for the actual concentration to approach the mean concentration.
The adaptation length and adaptation time represent the length scale and
time scale respectively.
For values of z a /h less than 0.01, the same values of a i and b i will be
used, because for smaller values the influence of z a /h on the adaptation
time and length is insignificant (Kerssens et al., 1979).
|
c
c e |
 
Search WWH ::




Custom Search