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How does COMSOL read data from text file?
Posted 05.03.2012, 14:17 GMT-5 Parameters, Variables, & Functions Version 3.5a, Version 4.2 6 Replies
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I set up a 3D COMSOL model, and several coefficients (Assume they are "A", "B", "C" and "D") are stored in a text file and should be evaluated at each node in each simulation step. Hence an interpolation function is used.
In COMSOL 3.5, I organize the text file in the following way:
% x y z A B C D
...
And when build a new interpolation function in COMSOL, A,B,C,D are automatically listed. The data type is "Unstructured".
However, in COMSOL 4.2, I have to choose a data type from "Grid", "Section Wise" and "Spreadsheet" before importing a text file. I think I should use "Grid". But when I import the same text file, COMSOL just cannot find those "A","B","C","D" parameters.
I check the rock_fracture_flow_aperture.mhp in the help document. And its text file is organized as follow:
% Grid
...
% Data
...
Question:
1) What type of data format should I use?
2) How to organize my text file?
Thanks
Dan
In COMSOL 3.5, I organize the text file in the following way:
% x y z A B C D
...
And when build a new interpolation function in COMSOL, A,B,C,D are automatically listed. The data type is "Unstructured".
However, in COMSOL 4.2, I have to choose a data type from "Grid", "Section Wise" and "Spreadsheet" before importing a text file. I think I should use "Grid". But when I import the same text file, COMSOL just cannot find those "A","B","C","D" parameters.
I check the rock_fracture_flow_aperture.mhp in the help document. And its text file is organized as follow:
% Grid
...
% Data
...
Question:
1) What type of data format should I use?
2) How to organize my text file?
Thanks
Dan
6 Replies Last Post 06.03.2012, 13:12 GMT-5
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Posted:
1 decade ago
I'm using version 3.5a. Maybe the grid format is different in two versions.
For 3.5a, the grid format looks like:
% grid
x1 x2 x3
y1 y2
% data
f1 f2 f3 f4 f5 f6
where f1 = f(x1, y1), f2 = f(x1, y2), f3 = f(x2, y1), f4 = f(x2, y2), f5 = f(x3, y1), f6 = f(x3, y2).
For 3.5a, the grid format looks like:
% grid
x1 x2 x3
y1 y2
% data
f1 f2 f3 f4 f5 f6
where f1 = f(x1, y1), f2 = f(x1, y2), f3 = f(x2, y1), f4 = f(x2, y2), f5 = f(x3, y1), f6 = f(x3, y2).
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Posted:
1 decade ago
I'm using version 3.5a. Maybe the grid format is different in two versions.
For 3.5a, the grid format looks like:
% grid
x1 x2 x3
y1 y2
% data
f1 f2 f3 f4 f5 f6
where f1 = f(x1, y1), f2 = f(x1, y2), f3 = f(x2, y1), f4 = f(x2, y2), f5 = f(x3, y1), f6 = f(x3, y2).
Thanks a lot.
Then what about "sectionwise" and "spreadsheet"?
In my text file, the (x,y,z) is not in a grid pattern, it's the coordinate of each node. Can I set up a format in COMSOL 4.2 like:
% x y z A B C D
just like what I did in COMSOL 3.5?
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Posted:
1 decade ago
Hi, the "spreadsheet" reads the data in the unstructed format you are asking for. Not the "grid" format.
I'm trying to do this myself, but no luck yet. What I really want is a grid format defined like Excel
x1 x2 x3
y1 f11 f12 f13
y2 f21 f22 f23
which I could do with the grid command except I have hundreds of rows and columns. I don't want to type those in as one infinitely long row, so I'm heading down the path of
x1 y1 f11
x2 y1 f12
etc, which is the spreadsheet format. This set-up loads trivially as an interpolation function....
Haven't been able to actually plot the data yet...
Regards, John
I'm trying to do this myself, but no luck yet. What I really want is a grid format defined like Excel
x1 x2 x3
y1 f11 f12 f13
y2 f21 f22 f23
which I could do with the grid command except I have hundreds of rows and columns. I don't want to type those in as one infinitely long row, so I'm heading down the path of
x1 y1 f11
x2 y1 f12
etc, which is the spreadsheet format. This set-up loads trivially as an interpolation function....
Haven't been able to actually plot the data yet...
Regards, John
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Posted:
1 decade ago
Hi, the "spreadsheet" reads the data in the unstructed format you are asking for. Not the "grid" format.
I'm trying to do this myself, but no luck yet. What I really want is a grid format defined like Excel
x1 x2 x3
y1 f11 f12 f13
y2 f21 f22 f23
which I could do with the grid command except I have hundreds of rows and columns. I don't want to type those in as one infinitely long row, so I'm heading down the path of
x1 y1 f11
x2 y1 f12
etc, which is the spreadsheet format. If/when I get it working I'll post.
Regards, John
OK, I think I should put my coordinates and parameters as follow:
x1 y1 z1 A1 B1 C1 D1
x2 y2 z2 A2 B2 C2 D2
...
But for the spreadsheet, we also need to set "Number of arguments". It should be an integer between 1 and 3.
What's the meaning of "Arguments" , the dimension of my model or the number of parameters?
Thank you and Have a nice day
Dan
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Posted:
1 decade ago
Hi, the "spreadsheet" reads the data in the unstructed format you are asking for. Not the "grid" format.
I'm trying to do this myself, but no luck yet. What I really want is a grid format defined like Excel
x1 x2 x3
y1 f11 f12 f13
y2 f21 f22 f23
which I could do with the grid command except I have hundreds of rows and columns. I don't want to type those in as one infinitely long row, so I'm heading down the path of
x1 y1 f11
x2 y1 f12
etc, which is the spreadsheet format. This set-up loads trivially as an interpolation function....
Haven't been able to actually plot the data yet...
Regards, John
I find the box before "Use space Coordinates as arguments", I think number of arguments equals to the dimension of my model. (x,y,z) means 2.
But what about the "Position in file"
% x y z A B C D
what is the the position of parameter A tnen, 1, 4 or something else?
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Posted:
1 decade ago
Hi, the "spreadsheet" reads the data in the unstructed format you are asking for. Not the "grid" format.
I'm trying to do this myself, but no luck yet. What I really want is a grid format defined like Excel
x1 x2 x3
y1 f11 f12 f13
y2 f21 f22 f23
which I could do with the grid command except I have hundreds of rows and columns. I don't want to type those in as one infinitely long row, so I'm heading down the path of
x1 y1 f11
x2 y1 f12
etc, which is the spreadsheet format. This set-up loads trivially as an interpolation function....
Haven't been able to actually plot the data yet...
Regards, John
I've successfully define the interpolation function! Thanks a lot.
The text file is like:
%x y z A B C D
...
I can plot this function right in COMSOL now.
Another problem:
When I want to call this interpolation function in COMSOL 4.2, it seems that I should write as " A(x,y,z) " instead of "A", and if Ais a matlab function, the input should be dimentionless: A(x[1/m],y[1/m],z[1/m]). Is this correct?