open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I have a channel with at the first extremity a vane (with a law of closure) and at the other extremity I have a tunnel. My channel has a length of 60m. I would like to study the intumescences in the channel after the closure of the vane.

I don't know what limit condition I can put in the second extremity.
I try :
-the same flow rate law than the first extremity, but the wave in section one (vane) and the wave in last section are the opposite (like in the mirror).
-a constant water level, but the wave in the second extremity is pratically non existent. I can explain this result.
-to put a reservoir with a constant water level in place of tunnel, but I haven't the wave frequency.

What the good way to modelize the intumescences in this type of configuration?

Thank you for your help.

CA

Hello,

One possibility for modelling the downstream boundary conditions is to add after the tunnel a sufficiently long reach in order to have no influence of the boundary on the area of interest.

Best regards

Thank you for your reply.

Further to your reply, I have two questions :
- with your solution the propagation of the wave (specially the reflection) is not represented of the best way?
- my tunnel is in charge so I can modelize it with Mascaret, in supposing that the limit condition is sufficiently away, what is preferable like limit condition?

Thank you for your reply.

Best regards,

CA

First point , with my solution the reflection is not represented . But what do you have after the tunnel : a new reach ?

Second point : With the fluvial kernel (subcritical), you can model flow in charge with the trick : Preissman slot.

A last question : Are your intumescences modelised with Shallow water equations ?

Best regards

NG

To answer at your questions :
- first: yes I have a new reach after the tunnel
- second: Yes I tryed the Preissman slot but I have a systematic error "Main channel wetted perimeter is not strictly positive at the cross-section : P1 = 0.10E-07" (P1 corresponding to the preissman slot)
I don't know how solve this problem.

- last: I didn't know that It was possible to use this type of equation with mascaret. Where I can find this option? and what this option bring with respect to the option by default?

Thank you for your help

Best regards,

CA

Hello,

I would like to study the propagation of primary and secondary waves in an upstream rectangular channel after the quick closing of a downstream valve.

In order to do this calculation, I created a simple model with:
a 10 000 m long rectangular channel,
an upstream boundary condition which is an hydrograph Q(t)
a downstream boundary condition which is a closing of valve Zing,Zsup=f(t)
code MASCARET 8 - unsteady transcritical

But when I start the calculation, the following message appears :
" Type for the open boundary # 2 <= 0 or > maximum value = 8 "

Could you please help to find a solution to correct this errors ?

Moreother, don't hesitate to give me some general tips to develop a "good" model.

PS : The file of the model is attached

Thank you for your help.

Regards, Stéphane

Dear Stephane,

For a simulation of a secundary wave, the douwstream boundary condition is a Hydrogramm (Q(T) - Q = 0 very fast - few seconds).
You have to use the transcritical kernel with non hydrostatic terms.

Best regards

NG