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Function of two variables
Posted Nov 18, 2010, 12:58 p.m. EST Structural Mechanics 9 Replies
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Hello,
I am using COMSOL Multiphysics 3.5a to simulate electrical conduction in silicon under high electric fields / temperatures. I am using the physics DC conductive media and Heat transfer by conduction. I also have COMSOL 4.0a but I am using 3.5a because it is familiar to me, so some help in either version would be appreciated. I am currently using a model for conductivity which only depends on temperature, and I would like to make this a function of two variables - temperature and electric field. However, I am have a difficult time setting up this function of two variables.
When I go to Options > Functions to create a new function from a Table, there are only two columns x and f(x), and I obviously need 3 columns x, y, and f(x,y). When I imported a 3 column text file as a function, it says the data type is Unstructured with Dimension 2D. The data is a .txt file with 3 columns of numbers separated by tabs, with no column headers just data. It does not let me view the data numerically or graphically. I have no idea how is it interpolating between the points, what the data actually looks like in COMSOL, which columns are being designated to what, etc.
I do not have an explicit function for conductivity as a function of temperature and electric field, but rather a set points of experimental data for a range of electric field and temperature values. It would be nice to enter these points in COMSOL and have it do some cubic interpolation of the 3-D plane (x = temperature, y = electric field, z = conductivity), just like how it interpolates a function of one variable. I could also do this in MATLAB though, and just import a large 3-column array of data, however I can't figure this out either.
I would very much appreciate some help in getting this function of two variables running for my simulations.
Thanks,
Adam
University of Connecticut
I am using COMSOL Multiphysics 3.5a to simulate electrical conduction in silicon under high electric fields / temperatures. I am using the physics DC conductive media and Heat transfer by conduction. I also have COMSOL 4.0a but I am using 3.5a because it is familiar to me, so some help in either version would be appreciated. I am currently using a model for conductivity which only depends on temperature, and I would like to make this a function of two variables - temperature and electric field. However, I am have a difficult time setting up this function of two variables.
When I go to Options > Functions to create a new function from a Table, there are only two columns x and f(x), and I obviously need 3 columns x, y, and f(x,y). When I imported a 3 column text file as a function, it says the data type is Unstructured with Dimension 2D. The data is a .txt file with 3 columns of numbers separated by tabs, with no column headers just data. It does not let me view the data numerically or graphically. I have no idea how is it interpolating between the points, what the data actually looks like in COMSOL, which columns are being designated to what, etc.
I do not have an explicit function for conductivity as a function of temperature and electric field, but rather a set points of experimental data for a range of electric field and temperature values. It would be nice to enter these points in COMSOL and have it do some cubic interpolation of the 3-D plane (x = temperature, y = electric field, z = conductivity), just like how it interpolates a function of one variable. I could also do this in MATLAB though, and just import a large 3-column array of data, however I can't figure this out either.
I would very much appreciate some help in getting this function of two variables running for my simulations.
Thanks,
Adam
University of Connecticut
9 Replies Last Post Apr 23, 2012, 2:58 a.m. EDT
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Posted:
1 decade ago
There must be a way to implement a function of two variables in COMSOL . . .
Has anyone done this before? Is there anyone who can help me?
Has anyone done this before? Is there anyone who can help me?
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Posted:
1 decade ago
I don't use the MatLab Link, but at least this would be the way to solve this problem. Working with COMSOL under MatLab. Then you should be able to use the buitl-in interpolation funtions of MatLab.
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Posted:
1 decade ago
Hi
have you read the chapter on "Analytical Functions" in the user "guide.pdf" of the 3.5a doc ?
--
Good luck
Ivar
have you read the chapter on "Analytical Functions" in the user "guide.pdf" of the 3.5a doc ?
--
Good luck
Ivar
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Posted:
1 decade ago
Hi,
It is possible to define a function of two variables using an interpolation function defined in a text file using the spreadsheet data format: the first column contains the values for the first input argument, the second column contains the values for the seond input argument, and the third column contains the function's value. Each row then contains a set of two input arguments and the corresponding function value:
x1 y1 f(x1,y1)
x2 y2 f(x2,y2)
...
The Spreadsheet data format is documented in the File Formats chapter of the COMSOL Multiphysics Reference Guide for version 4. I recommend using version 4, where you can get a preview plot by clicking the Plot button. COMSOL Multiphysics then shows a surface plot of the function in the Graphics window so that you can see the effects of the various interpolation and extrapolation options before using the function in the model.
Best regards,
Magnus Ringh, COMSOL
It is possible to define a function of two variables using an interpolation function defined in a text file using the spreadsheet data format: the first column contains the values for the first input argument, the second column contains the values for the seond input argument, and the third column contains the function's value. Each row then contains a set of two input arguments and the corresponding function value:
x1 y1 f(x1,y1)
x2 y2 f(x2,y2)
...
The Spreadsheet data format is documented in the File Formats chapter of the COMSOL Multiphysics Reference Guide for version 4. I recommend using version 4, where you can get a preview plot by clicking the Plot button. COMSOL Multiphysics then shows a surface plot of the function in the Graphics window so that you can see the effects of the various interpolation and extrapolation options before using the function in the model.
Best regards,
Magnus Ringh, COMSOL
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Posted:
1 decade ago
x y f(x,y)......
i have given in the above format and its showing the following error
Error: 6080
Interpolation grid axis values must be sorted in ascending order in each dimension
Exception:
com.femlab.jni.FlNativeException: Non monotonous interpolation grid
Messages:
Non monotonous interpolation grid
Stack trace:
at interpolator.cpp, row 408, ()
at com.femlab.xmesh.Xmesh.addElems(Native Method)
at com.femlab.xmesh.Xmesh.addElems(Unknown Source)
at com.femlab.commands.MeshExtendCommand.c(Unknown Source)
at com.femlab.commands.MeshExtendCommand.r(Unknown Source)
at com.femlab.commands.MeshExtendCommand.evalOnServer(Unknown Source)
at com.femlab.commands.FlCommand.runServerCode(Unknown Source)
at com.femlab.server.ServerProxy.eval(Unknown Source)
at com.femlab.commands.FlCommand.a(Unknown Source)
at com.femlab.commands.FlCommand.eval(Unknown Source)
at com.femlab.commands.a.a(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
i have given in the above format and its showing the following error
Error: 6080
Interpolation grid axis values must be sorted in ascending order in each dimension
Exception:
com.femlab.jni.FlNativeException: Non monotonous interpolation grid
Messages:
Non monotonous interpolation grid
Stack trace:
at interpolator.cpp, row 408, ()
at com.femlab.xmesh.Xmesh.addElems(Native Method)
at com.femlab.xmesh.Xmesh.addElems(Unknown Source)
at com.femlab.commands.MeshExtendCommand.c(Unknown Source)
at com.femlab.commands.MeshExtendCommand.r(Unknown Source)
at com.femlab.commands.MeshExtendCommand.evalOnServer(Unknown Source)
at com.femlab.commands.FlCommand.runServerCode(Unknown Source)
at com.femlab.server.ServerProxy.eval(Unknown Source)
at com.femlab.commands.FlCommand.a(Unknown Source)
at com.femlab.commands.FlCommand.eval(Unknown Source)
at com.femlab.commands.a.a(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
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Posted:
1 decade ago
Hi
the grid data must be ordered in increasing order if I remember right X first, Y after then f(x,y) pls check as as usual, I could be 50% off.
Try to save a data txxt file i.e. one from a material or a postprocessing plot and compare (2 dimensional)
--
Good luck
Ivar
the grid data must be ordered in increasing order if I remember right X first, Y after then f(x,y) pls check as as usual, I could be 50% off.
Try to save a data txxt file i.e. one from a material or a postprocessing plot and compare (2 dimensional)
--
Good luck
Ivar
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Posted:
1 decade ago
i have given it like
x y f...with x in ascending order and now the error is
Error: 9048
Format of data file is not correct.
It should contain grid and data values separated by lines starting with %
Exception:
com.femlab.util.FlException: Format of data file is not correct
Messages:
Format of data file is not correct
Stack trace:
at com.femlab.api.server.InterpElem.a(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.XFem.toElemSyntax(Unknown Source)
at com.femlab.commands.MeshExtendCommand.<init>(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
x y f...with x in ascending order and now the error is
Error: 9048
Format of data file is not correct.
It should contain grid and data values separated by lines starting with %
Exception:
com.femlab.util.FlException: Format of data file is not correct
Messages:
Format of data file is not correct
Stack trace:
at com.femlab.api.server.InterpElem.a(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.XFem.toElemSyntax(Unknown Source)
at com.femlab.commands.MeshExtendCommand.<init>(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
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Posted:
1 decade ago
i have given it like
x y f...with x in ascending order and now the error is
Error: 9048
Format of data file is not correct.
It should contain grid and data values separated by lines starting with %
Exception:
com.femlab.util.FlException: Format of data file is not correct
Messages:
Format of data file is not correct
Stack trace:
at com.femlab.api.server.InterpElem.a(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.XFem.toElemSyntax(Unknown Source)
at com.femlab.commands.MeshExtendCommand.<init>(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
x y f...with x in ascending order and now the error is
Error: 9048
Format of data file is not correct.
It should contain grid and data values separated by lines starting with %
Exception:
com.femlab.util.FlException: Format of data file is not correct
Messages:
Format of data file is not correct
Stack trace:
at com.femlab.api.server.InterpElem.a(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.InterpElem.toElemSyntaxes(Unknown Source)
at com.femlab.api.server.XFem.toElemSyntax(Unknown Source)
at com.femlab.commands.MeshExtendCommand.<init>(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.SolveModel.a(Unknown Source)
at com.femlab.api.client.x.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.j.run(Unknown Source)
at com.femlab.util.ae.run(Unknown Source)
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Posted:
1 decade ago
I had a similar problem trying to input values from a Cristy and Johnson table.
Turned out my problem(I got the first error message you got) was that there was one variable with a repeated value but different function value, ie
x1 f(x1)
1 5
1 6
You might want to go through your table in matlab or excel and just check you don't have any repeated values freaking the fit program out. You may have x in ascending order but if there's a repeated y value it might screw it up.
Did you sort this out? I need to do the same thing with 2 interpolations over a phase change.
Turned out my problem(I got the first error message you got) was that there was one variable with a repeated value but different function value, ie
x1 f(x1)
1 5
1 6
You might want to go through your table in matlab or excel and just check you don't have any repeated values freaking the fit program out. You may have x in ascending order but if there's a repeated y value it might screw it up.
Did you sort this out? I need to do the same thing with 2 interpolations over a phase change.