# hydrograph(B60) and Average velocity of initial section

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November 10, 2021, 08:33
hydrograph(B60) and Average velocity of initial section
#1
New Member

yangshihang
Join Date: Mar 2021
Location: hangzhou,china
Posts: 3
Rep Power: 3
I found that when average velocity of initial section (discharge)is higher ,the program will not go on.
For example ,when average velocity is 0.5 m/s, it goes well.when average velocity is 2.0 m/s, it stops emergently, in a few seconds(0.5~4 second).
I think i need "hydrograph.dat",help me to make water changes smothly.
So please give me an example.
AND here my text.
control
C 11 1
C 12 3
C 13 3
C 14 2
C 15 3
C 16 3
B 2 700 1 170
B 10 0.0 30.0 0.0 0.05 0.0 6.0
B 101 8
B 121 250 12.5 200 17.5 250
B 103 8
B 123 30 1.5 100 4.0 40
G 10 1
G 15 2
G 20 0
G 31 14
M 10 6
M 20 2
O 32 15 2.48 0.4
ctrl
B 10 1
B 50 0.0001
B 60 1
B 61 3
B 75 1
D 10 4
D 20 2
D 30 1
F 30 3
F 40 3
F 42 6.0
F 50 4
F 60 4.5
G 50 1
N 10 14
N 11 11
N 40 3
N 41 240
N 47 1.5
N 48 1
M 10 6
P 10 1
P 24 1
P 28 1
P 30 0.1
I 12 0
S 10 1
S 11 1
S 12 1
S 13 1
S 15 0
S 16 3
S 20 0.0030
S 24 0.5
S 30 0.004
S 41 2
S 42 2
S 45 40
S 46 1
S 50 3
S 60 0
S 71 5
S 72 25
S 77 3 26
S 80 0
S 90 1
S 91 2
T 10 2
T 36 2
W 10 0.25 (I only change here 0.05 or 0.25)
W 22 -9.81

AND here is my picture of different discharge,first one is result of (W 10 0.25);last one is result of (W 10 0.05)
Attached Images
 20.png (27.8 KB, 15 views) 05.png (106.1 KB, 13 views)

 November 10, 2021, 22:27 #2 Member   Ismael Incoencio Join Date: Sep 2021 Posts: 43 Rep Power: 4 Maybe it's not a question of the velocity, but of the WSE hitting the top of your domain. You screenshot for Q=0.25 shows it's already dangerously close to the top wall. Any increase in discharge would likely result in a deeper flow.

 November 12, 2021, 01:23 #3 Member   Ismael Incoencio Join Date: Sep 2021 Posts: 43 Rep Power: 4 On a related note, have you gotten the hydrograph.dat to work? I can't seem to get it running. __________________ Still learning

November 12, 2021, 04:23
#4
Super Moderator

Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 184
Rep Power: 15
Hi Yangshihang,

I think your inflow velocity is very high for this case, are you sure about the discharge?

What helps is to avoid the initial inflow surge by using I 10 1, which will initialize the whole domain with a potential flow solution. This seems to work, see attachment.
Attached Images
 flow.jpg (31.5 KB, 14 views)
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