open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello everyone,
I need to build a bridge with Telemac2d but I have some doubts and I hope someone could help me.
Because the water under the bridge could be at free surface or in pressure, I decide to represent it with a series of tubes.
I attached a pictures with the section of the bridge I would represent with Telemac (Picture1).
According to the section, I used 4 tubes.
The lenght of the pipe (L) is about 16 meters.
I attached another picture (Picture2) with the representation of the bridge in BlueKenue.
My doubts are about which values I should insert in the ASCII file.
In particular, these are the values I put in the file, could you please check if you notice something wrong?

I1 I2 Ce1 Ce2 Cs1 Cs2 Lrg Hau Clp L12 z1 z2
2132 3291 0.5 0.5 1 1 15.33 5.02 0 0.02 3.4 3.6
2421 2433 0.5 0.5 1 1 16.6 5.02 0 0.01 3.4 3.6
2313 5342 0.5 0.5 1 1 16.68 5.02 0 0.01 3.4 3.6
2172 4332 0.5 0.5 1 1 16.66 5.02 0 0.01 3.4 3.6


My doubts are the following:
1) Is it correct to choose these values of I1 and I2? I mean, in the manual there is written "I1 and I2 are the numbers of each end of the tube in the global point numbering system".
does it means that I1 and I2 are the center of the tube, or something else? in this case I have chosen the bottom level, but I think it is not correct.
2) Are the values of Z1 and Z2 correct?
3) In order to calculate L12 I have done as follow:
L12= lambda*(L/D) where: Lamdba value taken from the Moody diagram
L = 16 meters
D => (for the first tube) Area = 15.33 * 5.02 [m2] ---> but this is a rectangular section, so: Area=pi*((D^2)/4) --> D= 9.90 m

4) Until now I faced a rectangular section, but if I need to represent a section like the one in Picture3, where does the ASCII file take into account the differences, I mean, in which parameters?


Thank you all very much for your time and patience.
Daniele

Hello

1- as it is said explicitly in the manual, I1 et I2 are the numbers of the two nodes that match both ends of the tubes. For Telemac, this will give the path within which it will consider an (internal) flow between these two nodes.
2- it seems that Z1 and Z2 are correct
3- Yes also, for this point
4- you can estimate an equivalent height Hau (and/or equivalent width) Lrg corresponding to this section.

Also there are some ampirical formulae that you can use at the post-processing step in order to take into account for this particular geometry. See formula of Borda-Carnot for instance in the following references

M. CARLIER (1986). Manuel d’hydraulique générale et appliquée. Editions Eyrolles. (French)

US department of Transportation, Hydraulics of bridge waterways. Hydraulic design series

I hope that this helps

Riadh ATA

thank you very much!

I still have a doubt :)
It is about the width of the tube (Lrg).
In the ASCII file I only put the value, for example for the pipe connecting the node number 2421 and 2433 it is 16.60m (with the section of picture n°1).
My question is: where is the length located/considered to be? on the right, left of the selected node? or the node is considered to be in the middle of the length?
I attach a picture to clarify my doubt.

Thank you!

thank you very much!

I still have a doubt :)
It is about the width of the tube (Lrg).
In the ASCII file I only put the value, for example for the pipe connecting the node number 2421 and 2433 it is 16.60m (with the section of picture n°1).
My question is: where is the length located/considered to be? on the right, left of the selected node? or the node is considered to be in the middle of the length?
I attach a picture to clarify my doubt.

Thank you!

Hi
As the bridge is an artificial local solution to take into account the discharge as a local function of water level, there is no answer to your question!
As the inlet and outlet are manage by source point, we maybe could consider that we are more or less in the middle of the length.

The bridge management should be adapted to your model and your needs! This is the job of numerical modelers to determine what is the best solution for the problem at this specific place.
Imagine you have only 2 or 20 points in the minor bed of the river the bridge representation will not be the same even the bridge itself doesn't change!

Hope this helps

Good afternoon everybody,
I still have a question about the bridge representation.
I'm very poor with Fortran so I'd need your help to understand the BUSE.f file and to understand what telemac 2D does during the simulation with a bridge.

This is what I understood the buse.f file does (taking into account the attached figure (bridge)):





- There is a tube between node1 and node2.
- At a certain time, for instance T=300, there is a certain level of water in the river.
- For example at T=300 the water depth is constant in the area1 (see the picture) and the level is 1m (over the bottom surface).
- So telemac sees that above the node1 there is a water level of 1 meter.
- It evaluates if the water level in this node is > or < or = to the one of the node2 and evaluates if the the tube is in pressure or not.
- According to this last point, telemac applied the equations written in the buse.f file.
- For this example we could think that there is free surface water.
- So telemac evaluates the discharge flowing between node1 and node2 according to the head losses coefficients written in the tube file.
- As result telemac calculates the discharge flowing out form node2.
- So a discharge (and water depth, velocity, etc) "appears" in node2 and continues to flow downstream.

My questions are the following:

1) First of all I would like to have the confirmation of what I've already written, and so if I well understood the behavior of buse.f file.
2) If this is correct, it is like the water level (and other variables) of the node2 depends on node1. (I think they depend also from the other node that surrounded node2, but it is negligible now)
Because node1 is the node before node2 it is like the water flows between these two nodes. But what happen to other nodes??
For example node3: at time T=300 the water level is 1m. It is not connected with another node (to form a tube), so what happens to the water level at time T= (300+ timestep)? I think it increases because there is a wall (represented by the bridge mesh). And this happen also if I’ve chosen a very wide tube length (Lrg=length of the bridge).
So if my aim is to build a bridge without columns under the bridge, should I create as many tubes as to cover all the bridge section?
So "n" tubes where n= CrossChannelCountNode. (The parameter set in the channel mesh with Blue Kenue.)


Thank you in advance

Daniele

hello,
if someone has a few time could please answer to my last questions?

regards

Daniele