WUFI

Hello,

I am working with moisture sources in WUFI 2D and I would like to clarify the correct interpretation of the unit kg/(m·s) for the source strength.

From the documentation, I understand that WUFI multiplies the specified source strength by a length (not an area) and by the timestep duration to obtain the injected mass.

My question is: when I want to introduce a certain amount of water into one cell (defined by dx × dy), should I calculate the source based on the face length of the cell (dx or dy, depending on orientation), or should I use the full cell area (dx × dy)?

In other words, is the unit “per meter” referring to the third dimension (depth = 1 m in WUFI 2D), or does it refer to one of the face lengths in the 2D plane?

I want to make sure I am converting correctly from kg/m³ (water content) to the source input unit kg/(m·s).

Thank you very much for your clarification!

Best regards,
Mir Hedayat Moosavi

Hi Mir Hedayat Moosavi,

You have to multiply with dx, as long as your source is not related to a boundary, then it would be the dy for vertical boundaries.

The conversion is as follows, here as an example 100g/m² distributed over three month:
Conversion g -> kg: 100[g]/ 1000[g/kg]= 0.1 [kg]
Time period (t) -> 3600[s/h] * 2180[h] = 7848000 [s]
Source strength: -> 0.1 [kg] / 7848000 [s] = 1.2e-8 [kg/m²s]
Multiply that value with dx [m] to get [kg/ms]
2180h = three months

For WUFI 2d this has to be multiplied with the width of the distribution (see b here: viewtopic.php?p=3166#p3166.

Also see here:
https://wufi.de/en/service/downloads#2d_source_strength

Christian

Hi Christian,
Thank you for your response and the useful information.
Regards,
Hedayat