I am doing example of Biot poroelasticity with poroelasticity module, in the "Poroelasticity---------->poroelasticity material 1", why fluid properties should come from "fluid", but the porous elastic material property should come from "Domain material", why the porous elastic material property should come from "Porous1 or Porous 2"? Anybody who have done this example can tell me the reason?
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question on Poroelasticity module
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Phase calculation related error due to incorrect boundary conditions?
I am trying to simulate a metal insulator metal fishnet structure which in infinite in the yz plane and the TE polarized wave propagates in the z direction. I have applied PEC on the planes (xy planes) perpendicular to the electric field (Ez) and perfect magnetic conductor (PMC) on the planes perpendicular (xz planes) to magnetic field (Hy) . I then calculate the transmission and reflection away from the structure as shown in the attached image.
I am able to get the correct, transmission T= |t|^2 and reflection R= |r|^2, however, my extracted phase for the transmission (t) and reflection (r) are incorrect.
I tried the following
1. I used port boundary condition to excite and terminate the wave and PEC and PMC as described above to ensure the infinite periodicity in the yz plane. Why is the phase extracted from the S- parameter is not correct ?
2. I tried using scattering boundary to excite and terminate the wave with PEC and PMC as described. In this case, I could correct T but incorrect phase for the transmission. Reflection |R| was greater than 1, which is incorrect.
Can anyone tell me the correct boundary conditions and the means of exciting the wave?
Any help will be appreciated.
Thank you.
I am able to get the correct, transmission T= |t|^2 and reflection R= |r|^2, however, my extracted phase for the transmission (t) and reflection (r) are incorrect.
I tried the following
1. I used port boundary condition to excite and terminate the wave and PEC and PMC as described above to ensure the infinite periodicity in the yz plane. Why is the phase extracted from the S- parameter is not correct ?
2. I tried using scattering boundary to excite and terminate the wave with PEC and PMC as described. In this case, I could correct T but incorrect phase for the transmission. Reflection |R| was greater than 1, which is incorrect.
Can anyone tell me the correct boundary conditions and the means of exciting the wave?
Any help will be appreciated.
Thank you.
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Modeling a balloon to plug an opening
I would like to model a balloon used to plug the opening of an oddly shaped container. Ideally, the balloon would start uninflated, expand due to pressure and fill in the hole it is plugging. My intuition is to use contact pairs to look at the balloon-hole interaction. Is this the best approach for this model? Any feedback you can provide would be greatly appreciated.
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java exception error in using postcrossplot code.....
Hi
I am working in windows xp os and with Comsol 3.5a with matlab R2008b
I am exporting model file form comsol to matlab as fem and is saved in fem file in workspace. when iam using postcrossplot in order to save it and use it for meshintegrate code for integration on a particular cross section in a domain.
but when iam using code postcrossplot in matlab command window as follows
pd = postcrossplot(fem,2,[0.015 0 0;0.015 0 0.03;0 0.015 0]','surfdata','T')
extracting temperature data from subdomian in a particular cross section and storing it in pd variable....
it gives error as
??? Error using ==> figure
Error using ==> figure
Java exception occurred:
java.lang.NoClassDefFoundError: javax/media/j3d/BoundingBox
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
at java.lang.Class.privateGetPublicMethods(Unknown Source)
at java.lang.Class.getMethods(Unknown Source)
at com.mathworks.jmi.OpaqueJavaInterface.doesMethodExist(OpaqueJavaInterface.java:407)
Caused by: java.lang.ClassNotFoundException: javax.media.j3d.BoundingBox
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 5 more
Error in ==> gcf at 33
h = figure;
Error in ==> postnewplot>l_newplot at 27
currax = gca;
Error in ==> postnewplot at 15
hAx = l_newplot(vers);
Error in ==> postcrossplot at 368
ax = postnewplot;
I think it is problem with java files and help me regarding this.
thanks for your precious help in advance.
cheers
shanu
I am working in windows xp os and with Comsol 3.5a with matlab R2008b
I am exporting model file form comsol to matlab as fem and is saved in fem file in workspace. when iam using postcrossplot in order to save it and use it for meshintegrate code for integration on a particular cross section in a domain.
but when iam using code postcrossplot in matlab command window as follows
pd = postcrossplot(fem,2,[0.015 0 0;0.015 0 0.03;0 0.015 0]','surfdata','T')
extracting temperature data from subdomian in a particular cross section and storing it in pd variable....
it gives error as
??? Error using ==> figure
Error using ==> figure
Java exception occurred:
java.lang.NoClassDefFoundError: javax/media/j3d/BoundingBox
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
at java.lang.Class.privateGetPublicMethods(Unknown Source)
at java.lang.Class.getMethods(Unknown Source)
at com.mathworks.jmi.OpaqueJavaInterface.doesMethodExist(OpaqueJavaInterface.java:407)
Caused by: java.lang.ClassNotFoundException: javax.media.j3d.BoundingBox
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 5 more
Error in ==> gcf at 33
h = figure;
Error in ==> postnewplot>l_newplot at 27
currax = gca;
Error in ==> postnewplot at 15
hAx = l_newplot(vers);
Error in ==> postcrossplot at 368
ax = postnewplot;
I think it is problem with java files and help me regarding this.
thanks for your precious help in advance.
cheers
shanu
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CFD - Surface roughness
Hey guys
I really need your help on this one!
I was wondering if any of you could tell me about the default settings of surface roughness's in COMSOL?
All I've found about it in the documentation is Materials 3D Model Default Appearance Settings but I can't find anything about the use of surface roughness in the calculation of the pressure loss.
But the surface roughness does have an impact on the pressure loss however, I don't know where to find it nor do I know how to change it? Does COMSOL even use the material surface roughness or is it like Blasius --> surface roughness = 0?
Best Regards
Mikael
I really need your help on this one!
I was wondering if any of you could tell me about the default settings of surface roughness's in COMSOL?
All I've found about it in the documentation is Materials 3D Model Default Appearance Settings but I can't find anything about the use of surface roughness in the calculation of the pressure loss.
But the surface roughness does have an impact on the pressure loss however, I don't know where to find it nor do I know how to change it? Does COMSOL even use the material surface roughness or is it like Blasius --> surface roughness = 0?
Best Regards
Mikael
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Help with moving in Comsol.
Hello Mr. Ivar.
I am writing to you because you helped me to solve most of my problems.
Therefore, I would like to learn if you have any experience with choice
Physic Manager Builder.
And one more question:
When I use the AC / DC as MF create a magnetic field geometry where the driver is a magnet or coil.
I think that when an electrical conductor enters the magnetic field would have to move, but for me, nothing moves, even if I use time dependet study.
Thank you very much for your help and willingness.
Dipl.Ing Martin Kandl.
I am writing to you because you helped me to solve most of my problems.
Therefore, I would like to learn if you have any experience with choice
Physic Manager Builder.
And one more question:
When I use the AC / DC as MF create a magnetic field geometry where the driver is a magnet or coil.
I think that when an electrical conductor enters the magnetic field would have to move, but for me, nothing moves, even if I use time dependet study.
Thank you very much for your help and willingness.
Dipl.Ing Martin Kandl.
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Licensed number of users already reached.
Dear sir,
I am from IIT Madras and I am using an institute license. While opening the heat transfer module in COMSOL, it is saying "Licensed number of users already reached.". Can I know what the problem is? And, how can I solve it??
I am from IIT Madras and I am using an institute license. While opening the heat transfer module in COMSOL, it is saying "Licensed number of users already reached.". Can I know what the problem is? And, how can I solve it??
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UNDO
How to undo past actions in comsol 4.3a??
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Frequency domain with two input variables
Dear all
If I add a external force on one end of a silicon beam while let the other end fixed, is it possible to put a constant voltage across this beam in frequency domain simulation? It seems COMSOL4.2a set both external force and the voltage to AC (e.g. sinusoidal) form in default frequency domain simulation. But I want to keep the voltage unchanged. Does anyone know how to realize it? Thanks.
Regards
James
If I add a external force on one end of a silicon beam while let the other end fixed, is it possible to put a constant voltage across this beam in frequency domain simulation? It seems COMSOL4.2a set both external force and the voltage to AC (e.g. sinusoidal) form in default frequency domain simulation. But I want to keep the voltage unchanged. Does anyone know how to realize it? Thanks.
Regards
James
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give specific values for every mesh point of a boundary as boundary condition
hey everybody,
is it possibly to give different values for all points of the mesh on the boundary, respectively?
for example, just a vector containing as many values as i have boundary mesh points, or something including the coordinates/mesh point coefficients -- specifically, i want to use a solution of another study at one boundary as new boundary condition for another study, both at the same geometry+mesh. should be possible, no? (in fact, i want to use the old solution, but add to every value a time-dependent term, but this should work then as well.)
please let me know if you know anything helpful, thanks alot.
kind regards and all best,
sabine
is it possibly to give different values for all points of the mesh on the boundary, respectively?
for example, just a vector containing as many values as i have boundary mesh points, or something including the coordinates/mesh point coefficients -- specifically, i want to use a solution of another study at one boundary as new boundary condition for another study, both at the same geometry+mesh. should be possible, no? (in fact, i want to use the old solution, but add to every value a time-dependent term, but this should work then as well.)
please let me know if you know anything helpful, thanks alot.
kind regards and all best,
sabine
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sloshing tank problem with FSI
Hi all,
I have seen the sloshing tank problem.
I want to do same problem with fluid structure interaction that means interaction between fluid and container.
fluid exerts a pressure on the wall on the container and due to that the properties would be change.
any suggestions??
I have seen the sloshing tank problem.
I want to do same problem with fluid structure interaction that means interaction between fluid and container.
fluid exerts a pressure on the wall on the container and due to that the properties would be change.
any suggestions??
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initial value set-up
Hi,
I have a 2D simulation running from T=0 to T=100. First, I run the simulation from T=0 to T= 50. Then I want to use the solution at T=50 plus some value changes in specific domain as the initial value for my simulation from T=50 to T=100.
Can anyone help me out?
Another simple question is: can I find the solution value of variable PIP at T= 50 by PIP(t=50)? if not, how can I reference the variable at specific time point and/or spatial points as well?
Thanks in advance,
John
I have a 2D simulation running from T=0 to T=100. First, I run the simulation from T=0 to T= 50. Then I want to use the solution at T=50 plus some value changes in specific domain as the initial value for my simulation from T=50 to T=100.
Can anyone help me out?
Another simple question is: can I find the solution value of variable PIP at T= 50 by PIP(t=50)? if not, how can I reference the variable at specific time point and/or spatial points as well?
Thanks in advance,
John
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self-intersection
Dear all,
I'm trying to mesh a more or less complex structure and right now, I always receive the error message that self-intersection is not supported.
Can anyone explain this error message nearer to me? I don't know how to tackle this problem as I am not quite sure what its cause is.
Thank you.
I'm trying to mesh a more or less complex structure and right now, I always receive the error message that self-intersection is not supported.
Can anyone explain this error message nearer to me? I don't know how to tackle this problem as I am not quite sure what its cause is.
Thank you.
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Finding a mapping of Current Density (variable J) using the Electrostatics (es) Interface
Hi everyone,
I'm making a model using the Electrostatics Interface from within the limited AC/DC Module included with the base COMSOL Multiphysics package. Initially, I tried making my model using the Electric Currents (ec) Interface, but I was getting the 'wrong' answer (I will probably make a separate post for that problem, it would be interesting to see what you guys think about it). When I use the Electrostatics Interface, the answer I get is much better. The Electric Currents Interface includes the Current Density (J) variable from Ohm's Law, but the Electrostatics Interface does not.
Finding the Current Density (J) is relatively simple since the Electrostatics (es) Interface gives me the electric field (E). From Ohm's Law, I should easily be able to calculate J using: J = (sigma)(E). Where (sigma) is the electrical conductivity of the material (a vector/tensor quantity) and (E) is an electric field tensor.
How do I enter this into COMSOL? Is there a way to define this as a function somewhere? A variable? Or should I add this as another "physics" as some kind of PDE/ODE, even though it is only a matrix operation. Also, It may be hard to simply multiply an expression the sigma by E as sigma is a tensor/vector quantity and is unique to the material being modeled. The model is 2D and has two different materials in it, so the expression must take into account the E-field at that specific point and also the electrical conductivity associated with that point as well.
In case this post is too long for you to read or you don't understand the model after reading, I have attached it. It includes two different materials with assigned material electrical conductivities.
Thanks in advance for any help,
John
UPDATE: After some further investigation, I have found out that the Electrostatics Interface has an equation for x-direction current density as: es.Jx = es.Jdx. Where Jdx is the displacement current density, which happens to be zero for this modlue/model/interface. Investigating the Electric Currents Interface, the equation for equation for x-direction current density is: ec.Jx = ec.Jix + ec.Jdx. Where again, Jdx is displacement current density (again zero) and Jix is (ec.sigmaxx*ec.Ex+ec.sigmaxy*ec.Ey+ec.sigmaxz*ec.Ez) which is basically the Ohm's Law thing I was talking above where certain tensor quantities of of the electrical conductivity (sigma) is multiplied by the Electric Field (Ex, Ey, Ez). Why is there no induced current density in the Electostatics Interface? And when I try to add in the long expression for Jix in into the ex.Jx on the electrostatics I get an error saying that it doesn't know what es.sigmaxx, even though I have entered electrical conductivities for all materials I am studying.
I'm making a model using the Electrostatics Interface from within the limited AC/DC Module included with the base COMSOL Multiphysics package. Initially, I tried making my model using the Electric Currents (ec) Interface, but I was getting the 'wrong' answer (I will probably make a separate post for that problem, it would be interesting to see what you guys think about it). When I use the Electrostatics Interface, the answer I get is much better. The Electric Currents Interface includes the Current Density (J) variable from Ohm's Law, but the Electrostatics Interface does not.
Finding the Current Density (J) is relatively simple since the Electrostatics (es) Interface gives me the electric field (E). From Ohm's Law, I should easily be able to calculate J using: J = (sigma)(E). Where (sigma) is the electrical conductivity of the material (a vector/tensor quantity) and (E) is an electric field tensor.
How do I enter this into COMSOL? Is there a way to define this as a function somewhere? A variable? Or should I add this as another "physics" as some kind of PDE/ODE, even though it is only a matrix operation. Also, It may be hard to simply multiply an expression the sigma by E as sigma is a tensor/vector quantity and is unique to the material being modeled. The model is 2D and has two different materials in it, so the expression must take into account the E-field at that specific point and also the electrical conductivity associated with that point as well.
In case this post is too long for you to read or you don't understand the model after reading, I have attached it. It includes two different materials with assigned material electrical conductivities.
Thanks in advance for any help,
John
UPDATE: After some further investigation, I have found out that the Electrostatics Interface has an equation for x-direction current density as: es.Jx = es.Jdx. Where Jdx is the displacement current density, which happens to be zero for this modlue/model/interface. Investigating the Electric Currents Interface, the equation for equation for x-direction current density is: ec.Jx = ec.Jix + ec.Jdx. Where again, Jdx is displacement current density (again zero) and Jix is (ec.sigmaxx*ec.Ex+ec.sigmaxy*ec.Ey+ec.sigmaxz*ec.Ez) which is basically the Ohm's Law thing I was talking above where certain tensor quantities of of the electrical conductivity (sigma) is multiplied by the Electric Field (Ex, Ey, Ez). Why is there no induced current density in the Electostatics Interface? And when I try to add in the long expression for Jix in into the ex.Jx on the electrostatics I get an error saying that it doesn't know what es.sigmaxx, even though I have entered electrical conductivities for all materials I am studying.
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Magnetic field
Hello
I created a simple model where the magnetic field and electric wire.
1 Why not spread outside the magnetic induction coil?
2 Why is not moving conductor in a magnetic field?
What I made a mistake?
Thank you.
Goodbye.
I created a simple model where the magnetic field and electric wire.
1 Why not spread outside the magnetic induction coil?
2 Why is not moving conductor in a magnetic field?
What I made a mistake?
Thank you.
Goodbye.
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computing accurate fluxes with periodic boundary conditions?
Hi everybody,
does anyone know if I can compute the fluxes accurately, as described in the user guide on page 308 ff. and file 0973 from the knowdledge database etc, when using periodic boundary conditions on the respective boundaries? In the descriptions, it is explained only for Dirichlet boundary conditions :( And if you think it should work, should I then use the weak constraint option? (and, how, if you have time to explain?) I model in the PDE mode of version 4.1. with matlab.
All best,
Sabine
does anyone know if I can compute the fluxes accurately, as described in the user guide on page 308 ff. and file 0973 from the knowdledge database etc, when using periodic boundary conditions on the respective boundaries? In the descriptions, it is explained only for Dirichlet boundary conditions :( And if you think it should work, should I then use the weak constraint option? (and, how, if you have time to explain?) I model in the PDE mode of version 4.1. with matlab.
All best,
Sabine
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Electrostatics vs Electric Currents Interfaces. Something is wrong...
Hi everyone,
I mentioned this in an earlier post. I believe I have an inconsistency with the software (COMSOL Multiphysics Base Package). This may or may not be intended. When picking between the Electrostatics and Electric Currents Interfaces, I believe that the the basic functionality should be the same.
I have attached two different models of 3 copper "terminal" like objects in the middle of a relative insulator. I want to see the electric field and potential field mapped onto the geometry. One model uses the Electrostatics Interface and the other uses the Electric Currents Interface. Each model has a potential on the left terminal, ground on the right terminal, and nothing assigned to the middle terminal. Theoretically, the voltage should vary linearly from the potential to the ground with a little glitch in the linearity over the middle terminal. This is what the file "Electrostatics_ForumQuestion.png" file shows, which is the correct one. The other picture file "ElectricCurrents_ForumQuestion.png" shows an incorrect interpretation of the model (a non-linear change of the voltage with respect to the distance between the potential and grounded terminals). I have also included the corresponding Comsol model files for each one if you would like to see more.
Maybe I am missing something theoretically here. If these models do vary for some mathematical/physical reason (which I am obviously completely blind to :) ), could someone please explain to me why?
Thanks in advance for your time!
John
I mentioned this in an earlier post. I believe I have an inconsistency with the software (COMSOL Multiphysics Base Package). This may or may not be intended. When picking between the Electrostatics and Electric Currents Interfaces, I believe that the the basic functionality should be the same.
I have attached two different models of 3 copper "terminal" like objects in the middle of a relative insulator. I want to see the electric field and potential field mapped onto the geometry. One model uses the Electrostatics Interface and the other uses the Electric Currents Interface. Each model has a potential on the left terminal, ground on the right terminal, and nothing assigned to the middle terminal. Theoretically, the voltage should vary linearly from the potential to the ground with a little glitch in the linearity over the middle terminal. This is what the file "Electrostatics_ForumQuestion.png" file shows, which is the correct one. The other picture file "ElectricCurrents_ForumQuestion.png" shows an incorrect interpretation of the model (a non-linear change of the voltage with respect to the distance between the potential and grounded terminals). I have also included the corresponding Comsol model files for each one if you would like to see more.
Maybe I am missing something theoretically here. If these models do vary for some mathematical/physical reason (which I am obviously completely blind to :) ), could someone please explain to me why?
Thanks in advance for your time!
John
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Invalid Property Value "Lengthunit is a string" Error Message using Livelink Solidworks
I have this strange error message when I click on my geometry stating
Invalid Property Value
- Property: Lengthunit 'length unit' is a string
which I cannot get rid of. I think I do not have any length unit set in solidwork, any advice appreciated. Also, my physics results have totally wrong units, in meters, whereas I am working on a micron scale and I think this is related to the geometry error message.
Any help appreciated!
Erik
Invalid Property Value
- Property: Lengthunit 'length unit' is a string
which I cannot get rid of. I think I do not have any length unit set in solidwork, any advice appreciated. Also, my physics results have totally wrong units, in meters, whereas I am working on a micron scale and I think this is related to the geometry error message.
Any help appreciated!
Erik
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renew COMSOL license using a passcode
I downloaded the COMSOL 4.3a compact DVD image, double clicked it, then a "COMSOL 4.3a INSTALLER" interface showed.
When I clicked the "Change license" button, a window pop out that says "specify an existing COMSOL 4.3a folder". I used the default "C:\Program Files\COMSOL\COMSOL43a" and click open button. Then a massege that says "invalid destination folder. Wrong version of existing COMSOL 4.3a folder" showed up.
What's that means and how can I solve this problem? Thank you very much!
When I clicked the "Change license" button, a window pop out that says "specify an existing COMSOL 4.3a folder". I used the default "C:\Program Files\COMSOL\COMSOL43a" and click open button. Then a massege that says "invalid destination folder. Wrong version of existing COMSOL 4.3a folder" showed up.
What's that means and how can I solve this problem? Thank you very much!
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Non - Isotherma pipe flow
I am not able to find the "Non - Isothermal Pipe flow" module in my COMSOL 4.3a version. Can you help me out how to find it??
If not, I request you to help me with any method for simulating a pipe flow using "Non-Isothermal flow"? Thank you in advance...
If not, I request you to help me with any method for simulating a pipe flow using "Non-Isothermal flow"? Thank you in advance...
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