Geoscience Reference
In-Depth Information
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
upper limit proposed by Yen
et al.
(1985)
0
0.2
0.4
0.6
0.8
1
h
p
/H
f
Fig. 5.
Interfacial eddy viscosity versus flow depth ratio.
upstream. It is observed, especially in the backwater region, that the dis-
charge computed by the present method is larger than those by the divided
channel method (
ε
=0)andbyYen
et al
.
3
Now, numerical experiments are performed to see the impact of flood-
plain vegetation on the interfacial shear. A condition of submerged vege-
tation at vegetation density of 1.0 m
−
1
is assumed. The results are given
in Fig. 5, where the evaluated values of interfacial eddy viscosity are very
uniform regardless of the flow depth ratio. It can be seen in the figure that
the interfacial eddy viscosity is nearly constant (about 0.0004) irrespective
of the flow depth ratio.
A similar backwater computation is carried out for a compound open-
channel flow with vegetated floodplain. The vegetation density on the flood-
plainisassumedtobe
a
=1
.
0m
−
1
with
h
p
=0
.
3m and
c
D
=1
.
0. Other
computational conditions are the same as before. The discharge conveyed
by the floodplains is given in Fig. 6. A similar result is obtained that the
higher value of interfacial eddy viscosity results in larger discharge in both
uniform and nonuniform flow regions.
5. Conclusions
This paper investigated the impact of floodplain vegetation on the shear
layer in 1D apparent shear stress model for compound open-channel flows.
The mean flow and turbulence structures of the compound channel flows
were obtained using the 3D Reynolds stress model. It was found that the
evaluated friction slope due to interfacial shear is in good agreement with
