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Averaging

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Hello,

I run a diffusion test on a 3D model, I want to find average concentration over some cross sections along the x direction. is it possible?

Thank you,
Saeed

2 Replies Last Post 7 mars 2014, 08:38 UTC−5

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Posted: 1 decade ago 7 mars 2014, 04:36 UTC−5
Hello,
A simple solution (valid for a few and fixed sections) to this can be:
1. In Geometry:
a. Create a Work Plane where you want (for instance yz parallel, with x = x0).
b. Create a Partition (in Boolean Operations) with previous Work Plane.
2. In Definitions/Component Couplings: create an Average for the boundary (or boundaries) resulting from point 1.
3. Where and whenever you need it (as it has a global scope), you can use the average of corresponding quantity, for instance aveop1(c) in case of concentration (if you use the by default name for average operator).

You can do a more general approach creating two 'General Projections' (two, as this operation only allows to reduce the dimension in 1, and you need from 3D to 1D). One of them from 3D domain to a suitable boundary (for instance, an xy plane), and the other to project from that (2D) boundary to a suitable edge (better a straight line parallel to x). As each projection integrates (for you c) in the removed dimension, once done this, you only need to divide by section area, which could be a constant number (if not, you can compute it with the same operators).

Regards.
Jesus.
Hello, A simple solution (valid for a few and fixed sections) to this can be: 1. In Geometry: a. Create a Work Plane where you want (for instance yz parallel, with x = x0). b. Create a Partition (in Boolean Operations) with previous Work Plane. 2. In Definitions/Component Couplings: create an Average for the boundary (or boundaries) resulting from point 1. 3. Where and whenever you need it (as it has a global scope), you can use the average of corresponding quantity, for instance aveop1(c) in case of concentration (if you use the by default name for average operator). You can do a more general approach creating two 'General Projections' (two, as this operation only allows to reduce the dimension in 1, and you need from 3D to 1D). One of them from 3D domain to a suitable boundary (for instance, an xy plane), and the other to project from that (2D) boundary to a suitable edge (better a straight line parallel to x). As each projection integrates (for you c) in the removed dimension, once done this, you only need to divide by section area, which could be a constant number (if not, you can compute it with the same operators). Regards. Jesus.

Jeff Hiller COMSOL Employee

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Posted: 1 decade ago 7 mars 2014, 08:38 UTC−5
If you need that average solely for post-processing purposes, simply create a new dataset of the cut plane type and then compute the average via the Derived Values branch of the model builder (Surface Average on the dataset you just created).

If you need that average solely for post-processing purposes, simply create a new dataset of the cut plane type and then compute the average via the Derived Values branch of the model builder (Surface Average on the dataset you just created).

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