WUFI

Guten morgen fraunhofer person
I am simulating a suspended concrete slab with insulation to the underside.

To determined the starting moisture content for the concrete, I ran a simulation starting at 95%RH/20C for 3 months, then exported the kg/m3 profile data to use as starting conditions for the simulation when the insulation is installed.

Question 1: the only way I can find to use the "profile data" for the concrete and standard "80%RH/20C" conditions for the insulation seems to be to edit the .asc data file and add kg/m3 values for the insulation that correlate to "80%RH/20C" - is this correct?

Question 2: when I do the above, I seem to also have to edit the kg/m3 value for the last mm of concrete because the starting kg/m3 for the insulation reported in the "outcomes report" is much higher than the kg/m3 value nominated for "80%RH/20C"?

james bertram wrote:Question 1: the only way I can find to use the "profile data" for the concrete and standard "80%RH/20C" conditions for the insulation seems to be to edit the .asc data file and add kg/m3 values for the insulation that correlate to "80%RH/20C" - is this correct?

Hi James,
yes, you have changed the assembly by adding another layer, while the exported profile refers to the old assembly.

If you have added a new layer at the right side of the assembly, the old profile will be "too short", and WUFI will automatically repeat the last value of the existing profile to fill the new layer. If that's what you want, you don' t need to do anything else.

If you wish to use a different value for the initial water content of the new layer, you will have to edit the .asc file. If you want to use a constant value, add two new lines to the .asc file: one with an x-coordinate for the beginning of the new layer, and one with an x-coordinate for the end of the new layer. Specify the same water content for both coordinates, and WUFI will interpolate this (constant) profile to fill in the (constant) values for all new grid elements.

For example, if the old profile ends with
...
3.346923E-01 1.771149E+01
3.374976E-01 1.765782E+01
3.400000E-01 1.761166E+01

and you wish to add a 10 cm wide layer with an initial water content of 20 kg/m3, you could edit the file like this:
...
3.346923E-01 1.771149E+01
3.374976E-01 1.765782E+01
3.400000E-01 1.761166E+01
3.410000E-01 20
4.400000E-01 20


Specifying different water contents in the two new lines will result in a linearly varying profile across the new layer. Adding only the line for the "far end" of the insulation layer will result in a linearly varying profile, starting with the last value of the previously existing profile and ending at the newly added value.

If the new layer is not added to the right side of the assembly but inserted on the left side or in-between, you'll have to edit the x-coordinates of the existing profiles to reflect the shift in position. This could be done with a spreadsheet program.

Question 2: when I do the above, I seem to also have to edit the kg/m3 value for the last mm of concrete because the starting kg/m3 for the insulation reported in the "outcomes report" is much higher than the kg/m3 value nominated for "80%RH/20C"?

Maybe you specified only an initial water content for the "far" end of the insulation layer. WUFI then interpolates linearly between the last existing value (the last value in the concrete) and the value specified for the end of the insulation layer.

You can correct this by either adjusting that last value in the concrete as needed, or by inserting one line specifying the water content at the beginning of the insulation layer (as I did in the example above).

To see how WUFI interprets your edited .asc file, specify that file as initial water content file and choose "Run | Run calculation with film". WUFI then shows you the film screen with the initial profiles for temperature, relative humidity and water content. You can check whether these profiles are what you intended. Hover the cursor over one of the profiles to see its local value displayed in the status bar.

Regards,
Thomas

Hello Thomas - good to hear from you...and thank you for the detailed response.