↧
Another SPAM test
↧
What module to use to simulate the charge build up
I'm trying to visualize the charge building up and decaying on an electrode when different voltages are applied. For instance, theoretically charge should build up with time on an electrode when a positive voltage is applied and if the polarity be reversed the charge will decay with time. I'm trying to simulate this effect inside COMSOL. Can anybody help me on how to do this kind of a simulation. Should I be using an electrochemical module along with electrocurrents or eletrostatics to simulate this?
Thank You
Thank You
↧
↧
Plot
Hi every one,
I solve navier stokes equation with comsol 4.4 and got some basic plot? but really wanted to plot velocity field for y and x component velocities against arc length but after plotting am having my plot on the negative y direction which supposed not to be so. i need it in the positive y direction. Can any one help because, i have notting to do with negative values and the least value that i have is zero 0.
Cheers
George
I solve navier stokes equation with comsol 4.4 and got some basic plot? but really wanted to plot velocity field for y and x component velocities against arc length but after plotting am having my plot on the negative y direction which supposed not to be so. i need it in the positive y direction. Can any one help because, i have notting to do with negative values and the least value that i have is zero 0.
Cheers
George
↧
Need help with a degradable polymer simulation
Greetings
I'm trying to build a model of drug release from a bio material. The drug is carmustine which is released from the biodegradable polymer Gliadel wafer, which is implanted in the cavity resulted from the removal of a brain tumor.
Can someone please look at and tell me how to make a time-dependant simulation on it, what physics do I need?
Thank you
I'm trying to build a model of drug release from a bio material. The drug is carmustine which is released from the biodegradable polymer Gliadel wafer, which is implanted in the cavity resulted from the removal of a brain tumor.
Can someone please look at and tell me how to make a time-dependant simulation on it, what physics do I need?
Thank you
↧
Type of load in a wellbore
In order to apply fluid pressure in a casing I used roller support+boundary load , is this a right way to do it ?
Also for the formation I entered the sig_H, sig_h and sig_v as initial stress, just trying but not sure..!!
If anyone has any idea related to wellbore geomechanics load in Comsol please share. Please note that I dont have the subsurface flow module.
Adi
Also for the formation I entered the sig_H, sig_h and sig_v as initial stress, just trying but not sure..!!
If anyone has any idea related to wellbore geomechanics load in Comsol please share. Please note that I dont have the subsurface flow module.
Adi
↧
↧
Deformed geometry in 2D axial and 3D simulations.
Firstly, I would like to say hi to the comsol community, this being my very first post here.
My problem concerns DG and using it in 2D axial and 3D simulations.
I've made a model of a static permanent magnets system, using AC/DC Module Magnetic Fields, No currents Physics.
The image of the geometry is attached to this post.
I'm calculating electromagnetic force that acts on the inside pair of magnetic rings. The magnets are magnetized axially.
At the beginning the forces balance out. In 2D-axial, I can calculate the z component Fz that appears when I move the inner magnets in reference to the outer ones along the z axis (dZ displacement).
However, to calculate the radial component (x or y) Fr that appears while moving the magnets in the radial direction (x or y) I need a full 3D model.
I've created the 2D-axial model, according to the "Axial Magnetic Bearing Using Permanent Magnets" tutorial. As in this guide, I wanted to use a parametric sweep with a geometric parameter. The parameter is taken into account in my geometry as well as in the DG: Prescribed Mesh Displacement. I think that everything works as it should and via parametric sweep I get the same singular results as for the same parameter value without using DG and the sweep.
However, I've made a 3D model with the very same geometry and physics settings. When I use the radial displacement dR both in model geometry and DG I get different results using parametric sweep (2 times greater) than in the single step simulation for a certain value of dR without using DG. In my particular case, the function Fr(dR) is close to linear, so it looks like the distance is taken into account twice and therefore I get 2 times greater results.
On the other hand the magnetic flux density graph in the crossection plane zx (y=0) looks as if the dR is only accounted for once.
I tried refining the mesh, but the effect persists.
Could you please tell me what can be the case here? Do you have any idea why I do get different results? Should I take the displacement dR into account both in the geometry and DG in 3D? And if not, why is it different than in 2D axial?
I would really appreciate any help, because I need the simulation for my thesis.
My problem concerns DG and using it in 2D axial and 3D simulations.
I've made a model of a static permanent magnets system, using AC/DC Module Magnetic Fields, No currents Physics.
The image of the geometry is attached to this post.
I'm calculating electromagnetic force that acts on the inside pair of magnetic rings. The magnets are magnetized axially.
At the beginning the forces balance out. In 2D-axial, I can calculate the z component Fz that appears when I move the inner magnets in reference to the outer ones along the z axis (dZ displacement).
However, to calculate the radial component (x or y) Fr that appears while moving the magnets in the radial direction (x or y) I need a full 3D model.
I've created the 2D-axial model, according to the "Axial Magnetic Bearing Using Permanent Magnets" tutorial. As in this guide, I wanted to use a parametric sweep with a geometric parameter. The parameter is taken into account in my geometry as well as in the DG: Prescribed Mesh Displacement. I think that everything works as it should and via parametric sweep I get the same singular results as for the same parameter value without using DG and the sweep.
However, I've made a 3D model with the very same geometry and physics settings. When I use the radial displacement dR both in model geometry and DG I get different results using parametric sweep (2 times greater) than in the single step simulation for a certain value of dR without using DG. In my particular case, the function Fr(dR) is close to linear, so it looks like the distance is taken into account twice and therefore I get 2 times greater results.
On the other hand the magnetic flux density graph in the crossection plane zx (y=0) looks as if the dR is only accounted for once.
I tried refining the mesh, but the effect persists.
Could you please tell me what can be the case here? Do you have any idea why I do get different results? Should I take the displacement dR into account both in the geometry and DG in 3D? And if not, why is it different than in 2D axial?
I would really appreciate any help, because I need the simulation for my thesis.
↧
Evaluating integral results
I want to do some calculations using the results from surface integration in axi-symmetric mode. I am calculating the volume of some of the subdomains by just integrating 1 across the different volumes. The problems is that I want to evaluate the results from the integrals, but cannot find a way to extract these data from the results table.
For instance:
surf_a=surface integral of subdomain a
surf_b=surface integral of subdomain b
--> Evaluate surf_a/surf_b so I can see the result every time I run the model.
Thanks!
-William
For instance:
surf_a=surface integral of subdomain a
surf_b=surface integral of subdomain b
--> Evaluate surf_a/surf_b so I can see the result every time I run the model.
Thanks!
-William
↧
Flux Calculation
Hi all,
I am doing simulation for a problem that involves coupling between electrostatics and transport of diluted species.
In the problem I used "No Flux" condition for all species at one wall. I was able to obtain results. However, when I plot the total normal flux along that wall (with "chds.ntflux_c1" expression), the flux is NOT ZERO, not even close.
I refined the meshes near the wall but got the same problem.
Does someone know the reason and how to fix it? I am using 4.2a.
Thanks.
I am doing simulation for a problem that involves coupling between electrostatics and transport of diluted species.
In the problem I used "No Flux" condition for all species at one wall. I was able to obtain results. However, when I plot the total normal flux along that wall (with "chds.ntflux_c1" expression), the flux is NOT ZERO, not even close.
I refined the meshes near the wall but got the same problem.
Does someone know the reason and how to fix it? I am using 4.2a.
Thanks.
↧
Password cannot be entered into MATLAB LiveLink
Hi,
Whenever I try to start a MATLAB LiveLink (be it over the "COMSOL 4.4 with MATLAB" icon or manually) the command window lets me enter a username, but as soon as I want to enter a password, no entries are accepted. I can write whatever I want without it being shown in the command window. It thus becomes impossible to start a LiveLink application.
I am using COMSOL 4.4 and MATLAB 2014a. The MATLAB root is configured in COMSOL.
I would highly appreciate your help.
Thanks, Moritz
Whenever I try to start a MATLAB LiveLink (be it over the "COMSOL 4.4 with MATLAB" icon or manually) the command window lets me enter a username, but as soon as I want to enter a password, no entries are accepted. I can write whatever I want without it being shown in the command window. It thus becomes impossible to start a LiveLink application.
I am using COMSOL 4.4 and MATLAB 2014a. The MATLAB root is configured in COMSOL.
I would highly appreciate your help.
Thanks, Moritz
↧
↧
how to get the DEP force
Hi everyone
How to get the DEP force in the particle tracing module?
I add the DEP force in the particle tracing module and than study it.
But the errors are as follows:
Failed to evaluate variable Jacobian.
- Variable: freq
- Geometry: 1
- Domain: 5
Failed to evaluate operator Jacobian.
- Operator: env_pgeom_fpt
- Geometry: Particles
Failed to evaluate operator Jacobian.
- Operator: env_pgeom_fpt
- Geometry: Particles
I get the electric field data from the RF module
How to get the DEP force in the particle tracing module?
I add the DEP force in the particle tracing module and than study it.
But the errors are as follows:
Failed to evaluate variable Jacobian.
- Variable: freq
- Geometry: 1
- Domain: 5
Failed to evaluate operator Jacobian.
- Operator: env_pgeom_fpt
- Geometry: Particles
Failed to evaluate operator Jacobian.
- Operator: env_pgeom_fpt
- Geometry: Particles
I get the electric field data from the RF module
↧
Frequency response of displacement at a point -- maximum amplitude varies with frequency resolution
I am studying an example in the Model Libraries, the 'shear bender' under 'Structral Mechanics Module\Piezoelectric Effects'.
The example has only Stationary study.
I added a Eigenfrequency study, and found one of the resonant frequencies to be 19057.945Hz.
I then added a Frequency Domain study to see the ampliftude of displacement around 19057Hz.
I chose a point on the tip of the shear band to generate a 1-D plot of the displacement at that point.
I started with a frequency resolution of 50Hz, the plots looks fine, I can see the displacement peaks around the resonant frequency.
The problem is when I increase the freqeucny resolution from 50Hz, to 10Hz, 5Hz, 1Hz, the maximum value keeps increasing. This may be fine, if the system has high Q. At better resolution, I expect to see the peak increase to some extent. However, when I change frequency resolution from 0.1Hz to 0.5Hz, the amplitude jumped from 0.35mm to 4.5mm, more than 10 times! (I have attached a pdf file with the plots.)
The shear bender is used as example here. I noticed this issue in one of my own projects, in which a metal plate is being studied. At finer resolution, the maximum displacement also jumps like discribed above. Eventually the value obtained becomes unrealistic given the thickness of the metal plate. We are trying to compare the displacements at several resonant frequencies, but now it seems those results are questionable.
Can anyone share some thoughts on this? Thanks.
The example has only Stationary study.
I added a Eigenfrequency study, and found one of the resonant frequencies to be 19057.945Hz.
I then added a Frequency Domain study to see the ampliftude of displacement around 19057Hz.
I chose a point on the tip of the shear band to generate a 1-D plot of the displacement at that point.
I started with a frequency resolution of 50Hz, the plots looks fine, I can see the displacement peaks around the resonant frequency.
The problem is when I increase the freqeucny resolution from 50Hz, to 10Hz, 5Hz, 1Hz, the maximum value keeps increasing. This may be fine, if the system has high Q. At better resolution, I expect to see the peak increase to some extent. However, when I change frequency resolution from 0.1Hz to 0.5Hz, the amplitude jumped from 0.35mm to 4.5mm, more than 10 times! (I have attached a pdf file with the plots.)
The shear bender is used as example here. I noticed this issue in one of my own projects, in which a metal plate is being studied. At finer resolution, the maximum displacement also jumps like discribed above. Eventually the value obtained becomes unrealistic given the thickness of the metal plate. We are trying to compare the displacements at several resonant frequencies, but now it seems those results are questionable.
Can anyone share some thoughts on this? Thanks.
↧
flux conservation in transport of diluted species
Dear community,
I am trying to modelize the transport of ions through a membrane with Electrostatics and Transport of Diluted Species. The model is composed of 2 water chambers at each side of the membrane and a short micro channel between the membrane and one chamber. An electric potential is applied on top of one water chamber and I measure the current generated by the flux of ions in the channel. My problem is that the integrated total flux differs from the sum of diffusion flux and electrophoretic flux, and each one is different at the beginning and at the end of the channel, even though there is a non-flux boundary condition on the edge of the channel...
Does anyone have any ideas?
Let me attach the file. The integrated currents are in derivated values (hole sup and hole inf are respectively the entrance and exit of the microchannel).
Thanks,
Charlotte
I am trying to modelize the transport of ions through a membrane with Electrostatics and Transport of Diluted Species. The model is composed of 2 water chambers at each side of the membrane and a short micro channel between the membrane and one chamber. An electric potential is applied on top of one water chamber and I measure the current generated by the flux of ions in the channel. My problem is that the integrated total flux differs from the sum of diffusion flux and electrophoretic flux, and each one is different at the beginning and at the end of the channel, even though there is a non-flux boundary condition on the edge of the channel...
Does anyone have any ideas?
Let me attach the file. The integrated currents are in derivated values (hole sup and hole inf are respectively the entrance and exit of the microchannel).
Thanks,
Charlotte
↧
EC and MF coupling
Dear Community,
could pls somebody tell me how it is possible to couple the electric current interface with the magnetic field interface.
I tried it at a simple 3d model, made out of two aluminum tubes. At first I applied an normal current density Jn, like sin(2*pi*50[Hz]*t) at the wires, as boundary condition from the ec interface and added one ground terminal at the other ends of both wires.
After that I would like to use the variable "ec.Jn" as start-variable for the magnetic field interface. I used it at entry for the external current density domain condition ( it does not feel good in my mind, because I use a boundary condition as prestep for a domain condition - but there is no better variable, which would be nice to share with the magnetic field interface)..
At the end it doesn't work.
Could pls somebody give me a hint, how to couple the ec and mf interface effectively??
At the end I would like to calculate the Lorentz force, that's why I need the mf interface, as TIME DEPENDENT STUDY.
Or somebody could tell me how to couple the model starting at 7:40min www.youtube.com/watch?v=_QqX7oMAH2o
Many thanks in Advance..
Sven
could pls somebody tell me how it is possible to couple the electric current interface with the magnetic field interface.
I tried it at a simple 3d model, made out of two aluminum tubes. At first I applied an normal current density Jn, like sin(2*pi*50[Hz]*t) at the wires, as boundary condition from the ec interface and added one ground terminal at the other ends of both wires.
After that I would like to use the variable "ec.Jn" as start-variable for the magnetic field interface. I used it at entry for the external current density domain condition ( it does not feel good in my mind, because I use a boundary condition as prestep for a domain condition - but there is no better variable, which would be nice to share with the magnetic field interface)..
At the end it doesn't work.
Could pls somebody give me a hint, how to couple the ec and mf interface effectively??
At the end I would like to calculate the Lorentz force, that's why I need the mf interface, as TIME DEPENDENT STUDY.
Or somebody could tell me how to couple the model starting at 7:40min www.youtube.com/watch?v=_QqX7oMAH2o
Many thanks in Advance..
Sven
↧
↧
CFD,high mach flow
hi ,
i want to simulate a blunt body in high mach flow condition .high mach flow k-epsilon module used to simulate .but when inlet speed exceed from .8 mach number ,it give an error ,
how can i fix this problem ?
why work with this module is so difficult ?
i want to simulate a blunt body in high mach flow condition .high mach flow k-epsilon module used to simulate .but when inlet speed exceed from .8 mach number ,it give an error ,
how can i fix this problem ?
why work with this module is so difficult ?
↧
Surface Tension on Free Surface on 4.3a
Hi,
Im trying to set up surface tension on a free surface using Comsol 4.3a.
I am using single phase laminar flow and do not have access to the Microfluids module, which I understand easily implements surface tension, however I have been told the code has not changed from Comsol V3.5 in which even without the Microfluids module surface tension can be modelled.
Any help would be massively appreciated.
Thank you
Im trying to set up surface tension on a free surface using Comsol 4.3a.
I am using single phase laminar flow and do not have access to the Microfluids module, which I understand easily implements surface tension, however I have been told the code has not changed from Comsol V3.5 in which even without the Microfluids module surface tension can be modelled.
Any help would be massively appreciated.
Thank you
↧
PDE weak form-- multi dependent variables
I am using Weak form PDE(w) to solve a 2d problem. Actually I need 1 vector A=(A1,A2) and a scalar (b) to describe the weakform f(A1,A2,b,test(A1),test(A2),test(b))=0. And in Weak form PDE(w), I want use curl shape function for A and Lagrange shape function for b. But I saw that if I set 'Number of independent variables' to be 3, I cannot use curl shape function. If I set 'Number of independent variables' to be 2 for A, I cannot include b. What can I do? Thanks in advance!
↧
Heat Convection with Air and Water
Hello everybody,
im trying to do a simulation like in the picture below.
What i expect to see is natural convetion in the Air and Fluid based on the density change in the material.
I already did some simulations with natural convection in a one phase closed cavity, which worked really well.
My assumation to solve this problem is as followed:
1. Approach
- Laminar Flow for Air (spf1)
- Heat Transfer in Fluids for Air (ht1)
- non isothermal Flow for Air(nitf1)
- Laminar Flow for Water (spf2)
- Heat Transfer in Fluids for Water (ht2)
- non isothermal Flow for Water(nitf2)
But how can i couple these two things at the transition boundary (Boundary 1)?
2. Approach
- Heat Transfer in Fluids based on the material in the region ( Temperature Distribution without convection looks well)
But how can i specify the flow if i choose this approach?
With one laminar flow for air and water the solution does not compute right, maybe a problem with the boundary conditions?
If i do it with one laminar flow physic i specify the volumeforce as :
density_air*beta_air*g*(T-Treference)
or in the water region as:
density_water*beta_water*g*(T-Treference)
Is one of the approaches right? Or do i have to do it with the multiphase flow?
im trying to do a simulation like in the picture below.
What i expect to see is natural convetion in the Air and Fluid based on the density change in the material.
I already did some simulations with natural convection in a one phase closed cavity, which worked really well.
My assumation to solve this problem is as followed:
1. Approach
- Laminar Flow for Air (spf1)
- Heat Transfer in Fluids for Air (ht1)
- non isothermal Flow for Air(nitf1)
- Laminar Flow for Water (spf2)
- Heat Transfer in Fluids for Water (ht2)
- non isothermal Flow for Water(nitf2)
But how can i couple these two things at the transition boundary (Boundary 1)?
2. Approach
- Heat Transfer in Fluids based on the material in the region ( Temperature Distribution without convection looks well)
But how can i specify the flow if i choose this approach?
With one laminar flow for air and water the solution does not compute right, maybe a problem with the boundary conditions?
If i do it with one laminar flow physic i specify the volumeforce as :
density_air*beta_air*g*(T-Treference)
or in the water region as:
density_water*beta_water*g*(T-Treference)
Is one of the approaches right? Or do i have to do it with the multiphase flow?
↧
↧
COMSOL Equations about outputing coordinate of a contour
Dear All,
I am simulating a model where I hope to access the coordinates of a contour during simulation and update these coordinates into the model, which then continues to next time step. Does anybody know how to implement this process in COMSOL during simulation? I will be grateful if someone can help me tackle this problem.
Thank you so much in advance.
Zaibin
I am simulating a model where I hope to access the coordinates of a contour during simulation and update these coordinates into the model, which then continues to next time step. Does anybody know how to implement this process in COMSOL during simulation? I will be grateful if someone can help me tackle this problem.
Thank you so much in advance.
Zaibin
↧
CFD of air filter inside room (URGENT)
I am trying to model the air flow of a room with a filter box inside the room that has an inlet and outlet to it. However, the only information I have been able to find online to help me are vents that have an inlet from outside the room (i.e. HVAC). Could anyone possibly give me some advice about how to start modeling this air flow?
↧
Heat Transfer through a Multi-Layer Stack
Hi friends,
I'm very new COMSOL user and I am working on a project where I need to model a heat sealing process. This involves both thermal and mechanical deformation onto a multi-layer stack of materials. I am working in 2-D.
I am wondering how to go about beginning this process. I am thinking that there needs to be a contact interaction established between at least the 'heat seal press' and the topmost layer of the stack -- is that correct?
- Does there need to be contact established between all the layers?
- Is it possible to simulate the 'heat seal press' coming down onto the stack (simulating a heat seal process), ie a downward velocity with the heat seal press at a particular temperature?
- how do I make the bottom-most layer of the stack fixed (so that the whole stack does not move down from the pressure applied from the heat seal press)?
Any suggestions/tips? Any and all work be very much appreciated. Feel free to email me at mel.cantwell27@gmail.com
Thanks all,
Mel
I'm very new COMSOL user and I am working on a project where I need to model a heat sealing process. This involves both thermal and mechanical deformation onto a multi-layer stack of materials. I am working in 2-D.
I am wondering how to go about beginning this process. I am thinking that there needs to be a contact interaction established between at least the 'heat seal press' and the topmost layer of the stack -- is that correct?
- Does there need to be contact established between all the layers?
- Is it possible to simulate the 'heat seal press' coming down onto the stack (simulating a heat seal process), ie a downward velocity with the heat seal press at a particular temperature?
- how do I make the bottom-most layer of the stack fixed (so that the whole stack does not move down from the pressure applied from the heat seal press)?
Any suggestions/tips? Any and all work be very much appreciated. Feel free to email me at mel.cantwell27@gmail.com
Thanks all,
Mel
↧