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How to assign a 2D random function as porous matrix property (porosity)

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Good morning,

I really need your help, because I can't find anything in the help files.
I have a model using the the Brinkman Equations module for 2 dimensional porous media flow.
I want the porosity of the matrix to variate around the mean value of 0.5, so I defined a 2 dimensional random function named rn1 to describe this.

Now my problem is, that I can't define the porosity in the porous matrix properties as this rn function. I suspect, there is some kind of special "term" I have to use.
It would be great if you could help me!

Thank's a lot!

Jaques

4 Replies Last Post Jul 4, 2017, 9:23 a.m. EDT

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Posted: 1 decade ago Jul 4, 2011, 2:11 a.m. EDT
It would be great, if someone helps me with this problem. I'm stuck for about 2 days now.
It would be great, if someone helps me with this problem. I'm stuck for about 2 days now.

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Posted: 1 decade ago May 31, 2013, 3:05 p.m. EDT
Hi Jaques,

I have the same exact problem. I'm trying to simulate a random distribution of Quantum Dots in a dielectric material.
It looks like the graphics objects don't want to work with externally defined functions.

Did you ever solve it?
Hi Jaques, I have the same exact problem. I'm trying to simulate a random distribution of Quantum Dots in a dielectric material. It looks like the graphics objects don't want to work with externally defined functions. Did you ever solve it?

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Posted: 7 years ago Jul 4, 2017, 7:17 a.m. EDT
Hi Tal,

Did you solve the problem?
I met the same problem with now.
Thanks
Hi Tal, Did you solve the problem? I met the same problem with now. Thanks

Magnus Ringh COMSOL Employee

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Posted: 7 years ago Jul 4, 2017, 9:23 a.m. EDT
Hi,

It works, if you call it using "component syntax" in the text field for a user-defined porosity, such as

comp1.rn1(x[1/m],y[1/m])

if you have added a Random function called rn1 in Component 1 (comp1). The [1/m] syntax is used to make the input arguments dimensionless and hence avoid a warning about an unexpected unit of input.

Best regards,
Magnus Ringh, COMSOL
Hi, It works, if you call it using "component syntax" in the text field for a user-defined porosity, such as comp1.rn1(x[1/m],y[1/m]) if you have added a Random function called rn1 in Component 1 (comp1). The [1/m] syntax is used to make the input arguments dimensionless and hence avoid a warning about an unexpected unit of input. Best regards, Magnus Ringh, COMSOL

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