Differences in balance 1 and 2

[carolinarecart]

Hello,

I'm simulating an assembly using six different climates. In the first simulation cycle, I got over 20 convergence failures and significant differences in balance 1 and 2 in two climates, so I increased the grid and enabled the adaptative time control (steps 3, max stages 5). I re-ran the simulations and did not get any converge failure; however, the balance 1 and 2 were off from each other (more than one or digit differences). How can I increase the numerical quality of my simulations? I have to say the problems are for hot and humid climates, whereas the rest (cold and cool climates) results look fine. Is there any approach/advice I could follow?

Thanks in advance!

Carolina

[carolinarecart]

I was able to figure it out, for now. I just ran the simulation once for each file. I found that re-running the simulations increased the difference between the balances. Is this something that somebody else experienced?

For productivity (and my own sake), I save each file in a "non-simulation" folder and maintain that file as the key file. When I want to make modifications, I copy and paste that. Perhaps many people use this practice, but I haven't seen it mentioned in any of the WUFI manuals (maybe I haven't found it). It would be nice to know why, or if this is just me. Perhaps there are bugs in my software that I'm not aware of. Anyhow...

Thanks for reading

Carolina

[Christian Bludau]

Hi Carolina,
the differences in the balances you mention are related to convergence problems - WUFI has problems to distribute the water in the pore volume and numerical grid. And as this is an iterative procedure the differences may differ between two calculations. That does not happen, if the system can be solved.

This convergence problems are often related to materials with a low moisture storage function like air layers or mineral wool, as on the cold side they easily get supersaturated - and in this case the iteration is more difficult.

Please check out, if you can find positions, where dew water is forming. For air layers at the outside it may help to split them as described in this topic:
viewtopic.php?f=32&t=1777&p=5226#p5226

Christian

[carolinarecart]

Hi Christian,

There is dew water between the mineral wool and the sheathing layer in some climates I studied. I usually split the OBS or structural sheathing, but I didn't know about the air layer.
Thanks for the tip!

Carolina