Environmental Engineering Reference
In-Depth Information
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
Ir
In
NBI
ADFavg
ADFmin
0.1
0
-0.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
-1
-1.1
Figure 5.18
Comparison of I
r
, I
n
and NBI for increased PDD threshold pressure of net10
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Ir
In
NBI
ADFavg
ADFmin
-0.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
-1
-1.1
-1.2
-1.3
-1.4
-1.5
-1.6
-1.7
Figure 5.19
Comparison of I
r
, I
n
and NBI for increased PDD threshold pressure of net16
To be more confident with the last conclusion, another simulation has been run for all 16
optimised networks shown in Figure 5.1a-d and repeated by equalising the geometrical
properties of all the networks in the following way: the supply head of 70 msl in R1, the total
demand of 90 l/s allocated at
J2
,
J3
and
J4
(30 l/s each), all nodal elevations of 5 msl, all
pipe diameters of 250 mm, all distances to the demand nodes of 3000 m (the intermediate
nodes being located at the half of that distance, and all the k-values set at 0.5 mm.The PDD
threshold pressure was in all cases kept at 20 mwc.
The results of these two series of calculations shown in Figures 5.20 and 5.21 confirm the
observations from the previous figures. NBI follows the trend of
ADF
avg
but to a lesser extent
in the cases of larger difference between the
ADF
avg
and
ADF
min
values, as is the case of
net7
and
net8
in Figure 5.20. While the lower value of NBI for
net8
signals the problem caused by
the failure of major pipe, both resilience indices show higher resilience of this network. At
the same time,
net9
has lower values of
I
r
, and
I
n
, compared to
net8
, while the NBI (
ADF
avg
and
ADF
min
) are clearly higher in case of
net8
. Both observations lead to a conclusion that the
NBI values reflect the implications of the pipe failures more closely than the resilience
indices, in this example.
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