I am a beginner in comsol. could you please explain how the electric field pattern is being displayed even when we are not giving any input to the fibre.... is it just assuming a field..?
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tutorial model - step index fibre
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PCF design
How can I get imaginary part of effective mode index using comsol4.0 ? Help me.
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Input Port Excitation Power for 2D RF Simulation
Hello, I'm having difficulty understanding exactly what the input power is for the port in the RF module in COMSOL 4.3. The unit is declared as watt, but unless there's some predefined thickness, the unit doesn't make sense (I would expect watt/m).
Just as an example, I tried simulating a silicon waveguide and set a line integration variable on the input where I measured the emw.Poavx (perpendicular to the line) at different lines on the waveguide and multiplied this value (which is in watt/m) by my expected thickness and got values that were much smaller than what I expected for what I put in as my input power.
Does this mean that the unit for input power in the port excitation is in fact watt/m? If so, that would explain some discrepancies in my other results I've been simulating.
Just as an example, I tried simulating a silicon waveguide and set a line integration variable on the input where I measured the emw.Poavx (perpendicular to the line) at different lines on the waveguide and multiplied this value (which is in watt/m) by my expected thickness and got values that were much smaller than what I expected for what I put in as my input power.
Does this mean that the unit for input power in the port excitation is in fact watt/m? If so, that would explain some discrepancies in my other results I've been simulating.
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rigid particle carried by a channel flow
Hi
I have to simulate the displacement and rotation of a rigid prticule in a fluid flow and I am not a professional on comsol. So, is there anyone who could help me? or if you have any examples of this models.
Thanks
I have to simulate the displacement and rotation of a rigid prticule in a fluid flow and I am not a professional on comsol. So, is there anyone who could help me? or if you have any examples of this models.
Thanks
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Far field of dipole antenna on substrate
Dear COMSOL community
I try to model a nanodipole antenna on glass substrate , first I create a model for a nanodipole in air and the far field seems good to me ( the tours shape typical for dipole antenna ) , where the far field calculation is made by a surface surround the dipole and placed lamb/2 far away from the dipole.
Now I placed the dipole on the top of a glass substrate , while the far field domain this time will be half air and half substrate , unfortunately the shape of the far field seems to me incorrect , I read on the thread that the far field domain has to be homogeneous, but how to calculate the far field in the case of antenna placed on substrate
Thanks in advance
M.H.Elshorbagy
UCM , Spain
I try to model a nanodipole antenna on glass substrate , first I create a model for a nanodipole in air and the far field seems good to me ( the tours shape typical for dipole antenna ) , where the far field calculation is made by a surface surround the dipole and placed lamb/2 far away from the dipole.
Now I placed the dipole on the top of a glass substrate , while the far field domain this time will be half air and half substrate , unfortunately the shape of the far field seems to me incorrect , I read on the thread that the far field domain has to be homogeneous, but how to calculate the far field in the case of antenna placed on substrate
Thanks in advance
M.H.Elshorbagy
UCM , Spain
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Importing ASCII Geometry
I am completely new to Comsol so I really am struggling.
Can anybody explain how I can import some flat panel polygons I have defined as a series of x, y, z position vectors in ASCII into a Comsol file geometry.
I have used Matlab to create some CAD dfx files and tried doing an import. Everything looks like it is going fine then just get a "no geometry imported" error message. (See attached screenshot)
I also have Matlab LiveLink.
Any suggestions would be greatly appreciated,
Can anybody explain how I can import some flat panel polygons I have defined as a series of x, y, z position vectors in ASCII into a Comsol file geometry.
I have used Matlab to create some CAD dfx files and tried doing an import. Everything looks like it is going fine then just get a "no geometry imported" error message. (See attached screenshot)
I also have Matlab LiveLink.
Any suggestions would be greatly appreciated,
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A Swept Quad Mesh Within Free Tet - Quality Concerns
Hi everyone,
I'm looking for some advice on a meshing problem that I have - I have a heat load imposed on a 3D rectangular beam embedded within a larger beam of the same material; the two beams form a union. The area where the heat load is applied is very finely meshed with a mapped distribution so that I can control the exact number of elements in my area of interest.
This is great but my problem is that in order to cut down on computation time/memory cost - I am converting the boundaries of this swept block (or another swept block around it) to tri's and then putting in free tetrahedral mesh for the large remainder of the geometry. This has the unfortunate effect of creating a region of poor mesh element quality around the swept block where I need my mesh to be the most accurate.
I have attached an image of what the mesh element quality looks like in one iteration of this model. It seems that every time I try a slightly different meshing scheme - my results are significantly different and I have tried many variations. If anyone can suggest a better alternative to my current meshing scheme, or point me in the right direction of increasing the mesh quality, I would greatly appreciate it.
Finally, my heat loads are asymmetric and so unfortunately I cannot exploit any symmetry to cut down on the computational cost.
I'm looking for some advice on a meshing problem that I have - I have a heat load imposed on a 3D rectangular beam embedded within a larger beam of the same material; the two beams form a union. The area where the heat load is applied is very finely meshed with a mapped distribution so that I can control the exact number of elements in my area of interest.
This is great but my problem is that in order to cut down on computation time/memory cost - I am converting the boundaries of this swept block (or another swept block around it) to tri's and then putting in free tetrahedral mesh for the large remainder of the geometry. This has the unfortunate effect of creating a region of poor mesh element quality around the swept block where I need my mesh to be the most accurate.
I have attached an image of what the mesh element quality looks like in one iteration of this model. It seems that every time I try a slightly different meshing scheme - my results are significantly different and I have tried many variations. If anyone can suggest a better alternative to my current meshing scheme, or point me in the right direction of increasing the mesh quality, I would greatly appreciate it.
Finally, my heat loads are asymmetric and so unfortunately I cannot exploit any symmetry to cut down on the computational cost.
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Magnetic fields of moving objects
Hello everyone,
I am pretty new to COMSOL so this might be a simple question to answer.
I want to 2D simulate magnetic field distribution between a moving magnet and an iron bar. Stationary problem is solved easily. But when I want it to be time dependent, the fields don't move even though there are deformation indeed. So, the magnet moves but in the plot we have the distribution of the fields as in the solution of the stationary problem. I have tried to include Moving Mesh before the Solid Mechanics module but without success.
So my question is, how can I force the system to take into account spatial movement of the magnet in my problem so that it could be possible to show the changing of the field distribution in the resulting plots?
Can I do this only with the Physics “Magnetic Fields, No Currents”, "Solid mechanics" and "Moving Mesh" or do I need another physics?
Thank you very much!
Serg
I am pretty new to COMSOL so this might be a simple question to answer.
I want to 2D simulate magnetic field distribution between a moving magnet and an iron bar. Stationary problem is solved easily. But when I want it to be time dependent, the fields don't move even though there are deformation indeed. So, the magnet moves but in the plot we have the distribution of the fields as in the solution of the stationary problem. I have tried to include Moving Mesh before the Solid Mechanics module but without success.
So my question is, how can I force the system to take into account spatial movement of the magnet in my problem so that it could be possible to show the changing of the field distribution in the resulting plots?
Can I do this only with the Physics “Magnetic Fields, No Currents”, "Solid mechanics" and "Moving Mesh" or do I need another physics?
Thank you very much!
Serg
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Animated Magnetic Field of 3-Phase Cable
Hello,
I tried using the model "www.comsol.de/model/electromag...rrent-carrying-wires-131" to create a 3-phase cable carrying current with a 120° phase shift. I use the time domain and first I tried to set three different current parameters like " 6[A]*sin(2*pi*50[Hz]*t[s]+120[deg]) " and now I tried to use directly the term " 6[A]*sin(2*pi*50[Hz]*t[s]+120[deg])/(pi*r^2) " as external current density. But unfortunatley the resuting magentic field does not behave as expected. The attached .gif shows the magentic field, which is not correctly in phase. I also attached the .mph-file.
I want to use the time domain, because I want to animate the magnetic field. But I was wondering what the frequency domain can show me after calculation because when I shuld get an alternating field it showed e stationary field around each of the three wires.
Can someone help me?
I tried using the model "www.comsol.de/model/electromag...rrent-carrying-wires-131" to create a 3-phase cable carrying current with a 120° phase shift. I use the time domain and first I tried to set three different current parameters like " 6[A]*sin(2*pi*50[Hz]*t[s]+120[deg]) " and now I tried to use directly the term " 6[A]*sin(2*pi*50[Hz]*t[s]+120[deg])/(pi*r^2) " as external current density. But unfortunatley the resuting magentic field does not behave as expected. The attached .gif shows the magentic field, which is not correctly in phase. I also attached the .mph-file.
I want to use the time domain, because I want to animate the magnetic field. But I was wondering what the frequency domain can show me after calculation because when I shuld get an alternating field it showed e stationary field around each of the three wires.
Can someone help me?
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Phononic crystals
--i want to calculate the transmission spectrum for 2D solid solid phononic crystal and i am using solid module but i do not know what boundary condition i must use …
can any one know what boundary condition that help me to calculate the transmission coefficient ???
ahmed
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Analysis of mixed convection flows within a square cavity
Hi , I am new to the topic of solving mixed convection problems in COMSOL multiphysics.
I want to validate Fig. 8 of the paper(attached). Stream function and temperature contours for uniform bottom heating case with Pr = 10, Gr = 1000: (a) Re = 1, (b) Re = 10, and (c) Re = 100.
Which physics is to used here. Is it Laminar flow(SPF) and heat transfer(ht)?How to take care of Reynolds number in the governing equation? What is the body force or volume force to be used here? There is no Rayleigh number here but Grashoff number is the parameter of study here.
Kindly suggest for a non dimensional case.
Thanks in advance.
I want to validate Fig. 8 of the paper(attached). Stream function and temperature contours for uniform bottom heating case with Pr = 10, Gr = 1000: (a) Re = 1, (b) Re = 10, and (c) Re = 100.
Which physics is to used here. Is it Laminar flow(SPF) and heat transfer(ht)?How to take care of Reynolds number in the governing equation? What is the body force or volume force to be used here? There is no Rayleigh number here but Grashoff number is the parameter of study here.
Kindly suggest for a non dimensional case.
Thanks in advance.
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charge particle tracking assigning experimental magnetic field values to a magnet model
Dear All,
I have model of my magnet. I want to give it my own measured magnetic field and want Comsol to interpolate all missing values if it needs for the particle tracking. Can somebody tell if this is possible?
Regards,
Noaman
I have model of my magnet. I want to give it my own measured magnetic field and want Comsol to interpolate all missing values if it needs for the particle tracking. Can somebody tell if this is possible?
Regards,
Noaman
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Export comsol file( mph) to GDS FILE
Hi
Does anyone have idea on how to export (geometry) mph file (Comsol) to GDS file.
Need your help please.
thanks
Does anyone have idea on how to export (geometry) mph file (Comsol) to GDS file.
Need your help please.
thanks
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Piezoelectric transducer for liquids
Hi all,
I am using COMSOL to model a piezoelectric transducer directly coupled with liquid (oil or water) and using the tutorial provided in COMSOL website in this aspect. I am just defining one boundary of piezoelectric material as oscillating boundary (applied with voltage) and the other one grounded but am not sure about the results. Can any one answer a few queries regarding this?
- Are there any reflections of ultrasonic waves from liquid when placed in this way?
- How can I check the impedance matching characteristics of the piezoelectric especially the acoustic impedance?
- Can I change the phase or beam angle of piezoelectric transducer? If so, how?
- After having a look on the attached image, can some one explain the result and why I am getting this?
Many thanks in advance for any of your help.
I am using COMSOL to model a piezoelectric transducer directly coupled with liquid (oil or water) and using the tutorial provided in COMSOL website in this aspect. I am just defining one boundary of piezoelectric material as oscillating boundary (applied with voltage) and the other one grounded but am not sure about the results. Can any one answer a few queries regarding this?
- Are there any reflections of ultrasonic waves from liquid when placed in this way?
- How can I check the impedance matching characteristics of the piezoelectric especially the acoustic impedance?
- Can I change the phase or beam angle of piezoelectric transducer? If so, how?
- After having a look on the attached image, can some one explain the result and why I am getting this?
Many thanks in advance for any of your help.
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Acoustics - Large models convergence
Hi,
I'm driving crazy about this subject. I think don't know many things about this model, but regardless how mesh, solver configuration (multigrid, iterative, direct, etc.) or any other thing I change doesn't matters, it can't reach the convergence.
I'm trying to simulate the noise generated by a solid source that emits noise in all frequencies, like a power transformer, in an electrical distribution substation. I'm using the acoustics module in the frequency domain.
I don't know very well how to set the sources pressure (or the pressure level) with the boundary conditions. I'm using the "pressure" boundary condition setting an arbitrary pressure in order to perform a test.
I'm using an iterative solver with multigrid method (2 or 3 levels), with Krylov preconditioning. Then I use SOR or Jacobi methods.
No matter if set or not a parametric sweep (for frequencies), the solver not converge.
There's any "trick" or something that guides me to reach the convergence in these type of models?
Please, see the attached images in order to understand the described above.
Thanks in advance.
I'm driving crazy about this subject. I think don't know many things about this model, but regardless how mesh, solver configuration (multigrid, iterative, direct, etc.) or any other thing I change doesn't matters, it can't reach the convergence.
I'm trying to simulate the noise generated by a solid source that emits noise in all frequencies, like a power transformer, in an electrical distribution substation. I'm using the acoustics module in the frequency domain.
I don't know very well how to set the sources pressure (or the pressure level) with the boundary conditions. I'm using the "pressure" boundary condition setting an arbitrary pressure in order to perform a test.
I'm using an iterative solver with multigrid method (2 or 3 levels), with Krylov preconditioning. Then I use SOR or Jacobi methods.
No matter if set or not a parametric sweep (for frequencies), the solver not converge.
There's any "trick" or something that guides me to reach the convergence in these type of models?
Please, see the attached images in order to understand the described above.
Thanks in advance.
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Sheet metal bending - spring back effect
Hi
I am trying to make an elastoplastic 2D simulation of sheet metal bending to observe different spring back in various materials. I want to use V-bending proccess since we have a fixture to do the same experiment in the future to check for validity.
I would like to keep it as simple as possible. I am using some data that I have from tensile experiments for different materials and setting simple stress-strain curves with 3 points to vary the hardening. I also set the load/load removal along with auxiliary sweep for the load stepping so the spring back could be observed after the removal of the load.
I am not sure how I should define the contact between the parts. I tried to use contact pairs but I don't know if it is correct. Unfortunately cannot find much about this specific topic on the internet or in this forum (tried to use 3 point bending that someone used which could be similar but didn't succeed much)
I am trying to make an elastoplastic 2D simulation of sheet metal bending to observe different spring back in various materials. I want to use V-bending proccess since we have a fixture to do the same experiment in the future to check for validity.
I would like to keep it as simple as possible. I am using some data that I have from tensile experiments for different materials and setting simple stress-strain curves with 3 points to vary the hardening. I also set the load/load removal along with auxiliary sweep for the load stepping so the spring back could be observed after the removal of the load.
I am not sure how I should define the contact between the parts. I tried to use contact pairs but I don't know if it is correct. Unfortunately cannot find much about this specific topic on the internet or in this forum (tried to use 3 point bending that someone used which could be similar but didn't succeed much)
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Longer simulation study
Hello everyone,
I'm facing an usual problem with a comsol time dependent simulation study. In the study settings, upon changing the upper limit of the time range by a decade, the simulation doesn't show any physical response. While it was completely fine when the study setting was up to a certain limit in range, considering I didn't make any further changes in resolution or meshing in my physical model, going to one more decade level in the range doesn't produce any results. Could it be related to any other setting I might be unaware of?
To give you context I'm running a time dependent study of 0-10ms with a resolution of 1e-7 and relative tolerance of 1e-6. And I'm being able to run it when this range is 1ms but after that it just doesn't produce any result.
Any help would be appreciated.
I'm facing an usual problem with a comsol time dependent simulation study. In the study settings, upon changing the upper limit of the time range by a decade, the simulation doesn't show any physical response. While it was completely fine when the study setting was up to a certain limit in range, considering I didn't make any further changes in resolution or meshing in my physical model, going to one more decade level in the range doesn't produce any results. Could it be related to any other setting I might be unaware of?
To give you context I'm running a time dependent study of 0-10ms with a resolution of 1e-7 and relative tolerance of 1e-6. And I'm being able to run it when this range is 1ms but after that it just doesn't produce any result.
Any help would be appreciated.
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Propagation constant using port excitation
Dear All,
I have a question regarding the usage of propagation constant parameter for port excitation in the EM frequency domain simulation.
I tried to use the port functionality to excite an EM wave in a 2d geometry. I used a very simple rectangular geometry with PEC boundary conditions on the sides parallel to the x axis (length). The input excitation port was used on one of the side parallel to the y axis, with the user defined electric field as:
Ex=0, Ey=0, Ez=1.
1) Is the propagation constant defined always in the x direction (normal to excitation side).
2) If I assume that the propagation constant is in the x direction, I expect a phase shift in the Electric field vector for varying value (real) of propagation constant at any point in the x axis. However, I observed a change in magnitude (for emw.normE field) without any expected phase shift. Could you please help me to understand this?
Thanks,
Rahul
I have a question regarding the usage of propagation constant parameter for port excitation in the EM frequency domain simulation.
I tried to use the port functionality to excite an EM wave in a 2d geometry. I used a very simple rectangular geometry with PEC boundary conditions on the sides parallel to the x axis (length). The input excitation port was used on one of the side parallel to the y axis, with the user defined electric field as:
Ex=0, Ey=0, Ez=1.
1) Is the propagation constant defined always in the x direction (normal to excitation side).
2) If I assume that the propagation constant is in the x direction, I expect a phase shift in the Electric field vector for varying value (real) of propagation constant at any point in the x axis. However, I observed a change in magnitude (for emw.normE field) without any expected phase shift. Could you please help me to understand this?
Thanks,
Rahul
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selective laser melting_interface heat transfer
Dear all,
I am working on the simulation of SLM. I have a question, firstly laser irradiates on the surface of the metal, and I want to use the average temperature of the surface from coupling as the initial value of the surface temperature, in order to calculate the temperature driven flow effect. So actually how to realize this? Thanks in advance.
Greetings
I am working on the simulation of SLM. I have a question, firstly laser irradiates on the surface of the metal, and I want to use the average temperature of the surface from coupling as the initial value of the surface temperature, in order to calculate the temperature driven flow effect. So actually how to realize this? Thanks in advance.
Greetings
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Two phase Liquid Liquid extraction
Hello,
I am trying to model mass transfer through interface of two liquid in a two phase model. I believe comsol by default applies flux continuity at the interface. However I also want to an equilibrium boundary condition (governed by partition coefficient) at the interface. I used pointwise constraint to tie concentration c2-K*c1, where c1 and c2 are variables. As a results interface is not tracked properly and I get anomalous results for examples the phase fragments and no concentration value.
Can you please help me with this?
I am trying to model mass transfer through interface of two liquid in a two phase model. I believe comsol by default applies flux continuity at the interface. However I also want to an equilibrium boundary condition (governed by partition coefficient) at the interface. I used pointwise constraint to tie concentration c2-K*c1, where c1 and c2 are variables. As a results interface is not tracked properly and I get anomalous results for examples the phase fragments and no concentration value.
Can you please help me with this?
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