Negative diffusion viscosity detected

Dear all
Hi, I have a question recently. I would like to conduct a simulation experiment with the following parameter Settings. But it always reports a negative temperature. I tried to adjust a lot of parameters, I think that the problem is the activation energy and activation volume Settings. I’m a novice, so I don’t know if I’m right. I’d like to ask if someone can give me some advice. What direction should I go to modify the prm file, or is there any irregularities in my prm? Thanks.

paper.prm (3.5 KB)
world.txt (2.2 MB)


It’s not clear whether my question is a stupid question :joy:

Hi Wei,

If you use a very simple material model (ex: constant viscosity, density, thermal expansivity, etc), do you still get negative temperatures in your model?

Simplifying the model is a good way to start diagnosing the specific issue.

It’s not clear to me at first glance what your initial temperature conditions would produce. Maybe worth analytically checking to make sure your initial temperature function produces the expected values.


Thank you for your reply. I tried to set the activation energy and activation volume to 0 and adjust other parameters, so the model would not have negative temperature. like this:

So I feel that activation energy and activation volume is a big issue. But it is not clear whether the activation energy and activation volume and other parameters are involved. So I thought I’d ask someone else if they’ve ever been in a similar situation, or what they think. (Now I’m testing different activation energies and activation volumes, but I’m not sure if they’re useful for me)

Do you mean to have that inverted temperature field in your domain, with massive boundary layer thermal gradients?

That seems like a likely cause of numerical problems.

I agree with Bob, the temperature field structure is likely the root cause of the numerical issues.

Yean, It’s going to be a negative temperature. Thank you for your feedback. I’ll test the numbers and find the problems.