User Forum of Software BASEMENT

LydiaSeitz

User

Registered: 2014-09-08

Posts: 18

Implementation of gate

Hello everyone,

I have a gate in my model and I try to vary the gate level in order to calibrate the water level. But nothing happens when I vary the value. All the weirs are working just fine. As I understood, the gate level is the opening width of the gate. So if the opening width of the gate is 2m the gate level should also be 2m, or am I wrong? How comes the water level is not changing when I vary the gate level from 0.1 - 5m?

Did I understood anything wrong? I hope you could give me a tip.

Cheers,
Lydia

Christian Volz

User

Registered: 2014-09-04

Posts: 31

Re: Implementation of gate

Hi Lydia,

I am not sure that I understand your problem correctly. Probably the names of the input-tags are not chosen very clearly and lead to some confusion. The height of the gate opening a is calculated by the difference of two values, which must be given in the input file:

"gate_elevation" = upper part of the gate opening (Oberkante des Schütz) = Z_gate
"gate_level" = bottom level of the gate opening (Sohle) = Z_bott

The flux is computed as:
Q =area * [2*g*(H - mu*a)]^1/2

Q : discharge
b: width of the gate
a: height of gate opening (= Z_gate - Z_bott)
mu: contraction factor (vena contracta)
area: flow area = width of the gate multiplied by the height of the gate opening (= b * mu * a)
H: level difference between water surface elevation and gate bottom level ( = WSE - Z_bott)

It is also possible to specify time dependent values for  Z_gate and Z_bott in additional files.

Unfortunately I have found some wrong descriptions of the gate formula in the help text. I will correct these for the next bugfix release. If you have some problems with the meaning of the input parameters, do not hesitate to ask us.

Best regards
Christian

LydiaSeitz

User

Registered: 2014-09-08

Posts: 18

Re: Implementation of gate

Hi there,

sorry that I did not reply to the last answer, some other issues came in between. Now I am back working with the gate issue and I am afraid I still don´t get it.

I specified several input files for the gate opening and none of them are working. Here are some examples I already tried as input file:

#Time   H
x          x
x          x

#Time     Z_gate     Z_bott
x            x             x
x            x             x

Z_gate       Z_bott
x               x
x               x

In each case the model is not showing any changes in the water surface elevation. It does not even seem to implement any hydraulic structure.

Does anyone have an idea?

Cheers, Lydia

Valentina

User

Registered: 2016-01-08

Posts: 1

Re: Implementation of gate

Hello,
I have made some tests with BASEMENT (Version 2.5.3 R2396) to model the flow through a conduit located in a channel.  I have modelled it using a `gate´ type Inner_Boundary Block, which specifies the Z_gate level in an input file.

I have tried to check the results from the model applying the formula reported in this forum (Q =area * [2*g*(H - mu*a)]^1/2), but I don´t get the same results  that I have in the output file from BASEMENT.

Is this the correct formula implemented in the calculation or the model uses a different equation?

Thank you.

Best regards,
Valentina

Matteo Facchini

Developer

From: Trento

Registered: 2014-09-05

Posts: 278

Re: Implementation of gate

Hello Valentina,

for the formula I suggest you to look in the manual, there you find the information you are looking for!
(ref. to manual version 2.5.3 --> look in the reference, RII-Numerics Kernel, 2.3.4 Discretisation of Boundary Conditions)

Hope this helps,

Matteo