User Forum of Software BASEMENT

jiang

User

Registered: 2020-09-15

Posts: 12

Error

hi everyone
how to deal with the error:WARNING -> Mass conservation is not guaranteed! Negative water depth in element
   #13556 (slope = 0.0487836).

Matteo Facchini

Developer

From: Trento

Registered: 2014-09-05

Posts: 284

Re: Error

Hi

the error is self-explanatory: you are having issues with mass conservation. However, this is not an error, but a warning, does your simulation crash without any other message?

You should give us a little bit of context:

1. are you working with sediment transport?
2. do you have any structure/holes in your mesh?
3. is the element #13556 close to a boundary?
4. could you post a screenshot of the mesh in the surroundings of your element #13556?

Thanks!

jiang

User

Registered: 2020-09-15

Posts: 12

Re: Error

thank you for your reply.
1.I do simulate with bedload.but it appears no difference from that without bedload
2.I have no idea about whehter I have holes in my mesh
3.element 13556 is only one case ,but there are more than 300 elements.... but the simulation went well. I even ingored the warning.hh
4.by the way,I want to know what if I simulate the attenuation of waves so which hydraulics type should I choose?.
5.thanks again!

Matteo Facchini

Developer

From: Trento

Registered: 2014-09-05

Posts: 284

Re: Error

Hey,

so:

1. ok, then it is indeed an hdraulics problem. It is probably related to your mesh, but without seeing the mesh and the .bmc file it is hard to tell;
2. you should define holes in your mesh yourself, otherwise it is unlikely that you have them, refer to the tutorials to understand how to make holes in your mesh;
3. actually if you have mass balance problems it is not a good sign: do you results make sense?
4. With attenuation of waves you mean the effect of waves runup with diminishing water depth? There are specific numerical models for that, I am not sure if basement is suited for that. What you could do is to use a fixed water level downstream boundary condition to simulate the effect of a large water body at the downstream end of your watercourse.

I hope this helps,
cheers