open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi, im trying to model a benchmark i found but i dont know what the problem is. I dont have experience using this kind of programs but I need to know what is happening, I tried using the Second law of friction with a coefficient of 45. and it works fine but when I use Manning and 0.03 of coefficient it seems to be impossible to model. The water doesnt flow , is like a wall infront of them. I apreciate if any of you could help me.

the flow is 20 m3/s
the long of the channel is 1 km
the width is 10 m
the flow is subcritical at inflow and outflow with a depth of 0.748409
the manning roughness coefficient is 0.03

Hello,

I cannot open you archive for some reason, certainly due to my computer, but are you using friction law number 3 ? In this case it is the Strickler coefficient that is to be used, hence a coefficient 1/0.03, and Manning law is number 4, Chézy is number 2.

With best regards,

Jean-Michel Hervouet

Hi, I used friction law number 2 and it works just fine. But I need to use the friction law number 4 with a manning roughness coefficient of 0.03, when I simulate that it doesnt work it seems to be impossible and I dont know the reason of that. Check this files I´ll change the extension hoping you can have acces to them.

Thanks for the trouble

Hello,

OK, thus you are not just mistaking Strickler for Manning, so I do not know what happens. Could you try a Strickler law, number 3, with coefficient 1/0.03, which should be strictly equivalent with your test with Manning? Then I would need to run the case. Compared to law number 2, there is a dependency on the depth, so a mistake on the depth, with a very large depth for some reason could also be an explanation.

You can also remove STEERING FILE = ... from your steering file (it is not useful and can drive you mad if you change the name of the file and forget to change it inside).

You can also move to the pseudo-wave equation, which is much faster :

TREATMENT OF THE LINEAR SYSTEM : 2
SOLVER : 1

With best regards,

Jean-Michel Hervouet

I tried to do that but it doesnt give me de right values, Im comparing de results with an analytical problem to prove the performance of this great software, I will send you the image of the results and the exercise, I will apreciate all the help you can bring me, Im doing this for my tesis. Im comparing this software against Mike to prove that this one is better but to prove that I need to prepare a benchmark with an analitycal result and thats why im doing this. Can you help me with this? Thanks a lot for the help!

Hi,

just an idea. The water depth is for some analytical test cases near the critical depth (it looks like test case 1 is such a case). Small differences in depth (e.g. caused by different friction law) can trigger the inflow to be supercritical.

Maybe you can adapt the initial conditions, increasing the initial depth sometimes helps to avoid such problems.

Best regards,

Leo