WUFI Stainless Steel Material Question

ecs132 · Post by **ecs132** » Mon Mar 14, 2011 5:05 am -1100

I have been trying to run a 2D WUFI model and have run into an error that I am hoping to get help with. The assembly includes a metal stud wall. For the metal material I am using the stainless steel material that we created during the WUFI Advanced Workshop in Napa, CA.

The warning I am getting says:
“Warning: Bulk Density; out of range ]0..5E3] This might cause unexpected results!”

The material properties being used are:
-Bulk Density – 8000
-Porosity – 0.001
-Specific Heat Capacity 460
-Thermal conductivity 12
-Water Vapor Diffusion Resistance Factor 100000

Do you know what is causing this error and how it can be fixed? Any help would be greatly appreciated.

Manfred Kehrer · Mon Mar 14, 2011 7:10 am -1100

Hello E.Sohn,

I know you from the Seminar!

just ignore this Message.

You might run in some stability problems if you use non absorptiv and vapor tight material. In this case try in increase the moisture absorption as well as the vapor permability to have better results.

ecs132 · Post by **ecs132** » Tue Mar 15, 2011 6:03 am -1100

Thank you for the response; however...
We are trying to run a 2D model and cannot get it to produce results. We built the model and when we select “run” the calculations finish in less than a second and there are no results. We are finding one error notice in the “grid” tab. It is saying that some of our elements have a thickness of 0. The element which appears to be giving the error is the vertical portin of our steel stud ( (vertical in respect to how drawn on screen. This is the web of the stud that is perpendicular to the wall). These elements are modeled with a thickness of 1mm. Could this error be causing the calculations to not work correctly? And if so, do you have any suggestions for solving it?

I am unable to delete the layer in the grid selection or to add a width to it. When I delete the steel stud in the geometry selection the 0-width layer goes away and the error then indicates another laye is 0-width, which correspondes to another vertical steel stud location.

Thank you.

Erik

Christian Bludau · Tue Mar 15, 2011 8:42 pm -1100

I send you a PM...

agerman · Post by **agerman** » Mon Jan 14, 2013 7:43 pm -1100

I am having the same problem. I receive the error about the material properties out of range and I notice that I have elements defined in the grid which are of a zero width. Could you please post what the resolution is?
Thanks.
Alea

Christian Bludau · Mon Jan 14, 2013 8:48 pm -1100

WUFI 2D has some problems handling coordinates smaller then one mm. Half a mm will probably work. But if youo use elements like x.3 mm or something like that, the grid generation can fail. So you should create your construction the way, that there are no values smaller than one mm.

If you like to use memebranes for example, all the values in our database are adapted to use them with a thickness of 1mm.

Christian

agerman · Post by **agerman** » Tue Jan 15, 2013 10:47 am -1100

Thanks for the help. I did have a thin membrane in there which I increased to 1mm. That solved the problem initially but as I continued building my model I came across the error again which warns that there are elements with a thickness of zero. However, this was resolved by changing "/mm{1 mul}" to "/mm{10 mul}". If I understand it correct this increases the grid size from 1 to 10 per mm.
Thanks again.

Christian Bludau · Thu Jan 17, 2013 12:30 am -1100

Hello,

please be careful, this has nothing to do with the grid size:

However, this was resolved by changing "/mm{1 mul}" to "/mm{10 mul}". If I understand it correct this increases the grid size from 1 to 10 per mm.

It defines the factor from your unit to milimeter. So if you change that from 1 to 10, all your dimensions are factor 10 bigger - you are entering your dimensions in cm!!!

Christian