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Export surface current density from mef model

August 28, 2017, 3:42 pm
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Hi, could anyone help me out with a way to export surface current density from Magnetic and Electric Fields model?

I'm trying to simulating the magnetic field generated by a group of thin wires and a sample on top of it. Because the wires are too thin to generate 3D meshing in it, I used surface current boundary condition to deal with it. But after study, I found no way to export the surface current density of the wires.

Attached is my model.

Best,
Naijun
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question about boiling water

August 28, 2017, 6:08 pm
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Hi, thx for reading my request.

In 4.3 version there is a cfd example named boiling water, but when i apply it in version 5.2a, a problem happened which is about the weak contribution "test(psi)*phi_source+test(p)*usource", i don't why, and i attach the pdf of the cfd model below.

It's better someone has a complete model about boiling water, u can send it by email, my email address :516505956@qq.com.

Thx a lot!
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Appropiate meshing for a geometry

August 28, 2017, 7:41 pm
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Hi fellows, i'm currently working in an analysis of a human jaw, however i have got several doubts, some of them are those:
1- I have read that for some 3D constructions it's better remove any operations like rounding etc, now for the jaw, it have a lot of irregular surfaces, that could be a problem?
2-How can i use an adaptive mesh or where can i find the option in the comsol program? It is different for the 5.2a that the 5.3?

And like an additional ask, somebody knows where can i find the mechanical characteristics of the human raw or human bones, all that is for academical use and is too for independet study.
Pd: Please excuse if i have written something wrong or if i have use one or several words in a bad way, i'm still a newcomer to the english envyroment and the comsol use.
Thanks, i'm hoping for your answers.
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Modelling adhesion in solid mechanics

August 28, 2017, 10:13 pm
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Do any one have a worked out example for adhesion between two surfaces in contact? Please share

Thanks and Regards

Sreeram R
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Solver stucks at initial time step

August 29, 2017, 12:41 am
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Dear all,

I'm trying to use an external model for material behavior of ferromagnetics. When I call the model via a .dll-file, the solver gets stucked at the initial time step. When I use COMSOL as Remote-Debugger within Visual Studio 2017, I can see that the solver doesn't leave the initial time step. The only output I get from the solver is "Matrices are assembled". Has anyone else experienced that kind of problem? I'd be grateful for any kind of support. Thanks in advance.
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Modeling Piezoelectric Devices in 2D (Quartz)

August 29, 2017, 7:33 am
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Hello all,
I'm trying to model a AT-cut quartz in 2D. I have no problem working in 3D (similar to the thickness shear oscillator example: www.comsol.com/model/thickness...ar-mode-quartz-oscillator-4707), but something about the choices of coordinate systems in 2D is throwing me off.

In 3D i use a Euler angle (ZXZ) of (0,-54.75,0)[deg] with the LH IEEE 1978 material properties and my simulations have the desired results. In this simulation my quartz is a cylinder with the thickness in the global Z-direction, just like the previously mentioned example.

In moving to a 2D simulation, I want to capture the shear deformation that is in the X direction on a cross section of the crystal. I'm strugging getting the material orientation correct without use of the 3D Euler angles. Any assistance would be greatly appreciated.
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Restart simulation with particles already in the domain

March 13, 2012, 9:14 am
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Hello there,

I have another question regarding the particle tracing module. I have a model consisting of a Laminar Flow (chns) and a Particle Tracing for Fluid Flow (fpt) interfaces. Assume that I solve first the fluid flow without solving for the particles’ position and that my inlet flow rate is periodic (let’s say with period is one second). I then introduce on the inlet a distribution of particles that are released every 0.1 s and I run the particle tracing for one period. My problem comes when I want to restart the simulation for the particle tracing in order to calculate the fate of the particles during the next 1 second – now I have the particles that were already in the domain at the end of the previous calculation plus the ones that are released every 0.1 s during this new calculation. I cannot figure out how to do that, simply saying to the solver to use as initial condition the previous solution gives an error in the stiffness matrix.

Anyone has an idea?

Thanks in advance, J
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Can not open Comsol with "An unexpected error occurred"

February 4, 2015, 2:20 am
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hi everyone

Yesterday, I used Comsol normally, but today I can not open it anymore. It gives me this error and its details:

"An unexpected error occurred."

'.', hexadecimal value 0x00, is an invalid character.
at System.Xml.XmlEncodedRawTextWriter.InvalidXmlChar(Int32 ch, Char* pDst, Boolean entitize)
at System.Xml.XmlEncodedRawTextWriter.WriteElementTextBlock(Char* pSrc, Char* pSrcEnd)
at System.Xml.XmlEncodedRawTextWriter.WriteString(String text)
at System.Xml.XmlWellFormedWriter.WriteString(String text)
at System.Xml.Linq.ElementWriter.WriteElement(XElement e)
at System.Xml.Linq.XElement.WriteTo(XmlWriter writer)
at System.Xml.Linq.XNode.GetXmlString(SaveOptions o)
at Comsol.Command.BridgeCommand.ToCommandString()
at Comsol.Communication.ChannelBasedCommandManager.SendCommand(OutgoingCommandHandler commandHandler)
at Comsol.Communication.BridgeCommandManager.OutgoingCommandHandler.Run()
at Comsol.Communication.BridgeCommandManager.RunAndWait(BridgeCommand command)
at ComsolDesktop.MainWindow.StartJava(Boolean debug, Boolean devPlugins, NDisconnectInfo disconnectInfo, IBridgeCommandManager oldMgr)
at ComsolDesktop.MainWindow.StartJava(Boolean debug, Boolean devPlugins)
at ComsolDesktop.App.OnStartup(StartupEventArgs e)
at System.Windows.Application.<.ctor>b__1(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

is there anyone has some ideas about this problem ?
Many thanks
Duc
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Module Combination

September 14, 2015, 2:39 am
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Hi,
I am wondering whether I can couple the piezoelectric and RF module, in order to analyze the interaction between piezoelectric response and electromagnetic fields present in the medium?
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How to extract many coordinates in geometry?

August 25, 2017, 2:03 am
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Hi, I'm trying to extract the coordinates of several points and more importantly, I need to assign their coordinates as a variable.

Let's simplify it.
There is a random function (has a value between 0 and 1) and i'd like to find where(value>=0.9) and their coordinates and finally want to assign as variable.

1. coordinates of several points.
2. set up a new variable with their coordinates.

How could it be possible? I've been working for a month.
any suggestion would be thankful and whether it need to use livelink or not doesn't matter

Best regards.
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Comsol with matlab error on HPC cluster

August 25, 2017, 8:59 pm
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Dear All,

I run my comsol models with matlab on HPC cluster which have CentOS Linux installed on it. I use the following command for starting Comsol server on HPC

comsol mphserver &

This command starts Comsol server successfully but when I start connecting matlab to it by the following commmand:

matlab -nodesktop -nosplash -r "mphstart; mymfile.m; exit",

there appears an error which say: "Comsol server must run before calling mphstart", while I am sure about starting Comsol server, even when I try to start Comsol with Matlab by the command:

comsol mphserver matlab

server starts and runs Matlab but a confusing java error occurred and further processing is blocked.
FYI, I use Comsol version 5.3, It is interesting to inform you that everything is OK on my laptop with Windows 7. These errors occurs when I try to perform my simulations on HPC.

Any suggestions and helps are appreciated, Thanks,
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problem in implementing laminar inflow as BCs in 5.2

August 26, 2017, 5:47 am
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Hello friends,

I have built a microfluidic model in COMSOL 5.2. It's a basically 2D long pipe. I tried to use 'laminar inflow -> flow rate' and 'laminar outflow -> pressure' as inlet and outlet BCs respectively. But the software failed to give an answer. Instead, if I specified pressure at both boundaries, then it succeeded to give a result. So how can I use the 'flow rate' as an inlet BC properly?
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Unstable system matrices coming from extraction using Livelink with MATLAB

August 29, 2017, 11:31 pm
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I build an active magnetic bearing model in COMSOL 5.1 using AC-DC and studies of which are giving me results. After that, I have extracted the coordinate details from the model using Livelink with MATLAB. In this programme, [meshstats,meshdata]=mphmeshstats using this command, i have extracted the mesh details (node information and element matrix).The programme you will get in the name of getdata1.m in the attachment. Then I have tried to extract the state space system matrices using mphstate command. The program you will get in the name of statespace1.m in the attachment. For that, I had to create one domain probe point. I am taking one node position( x,y,z coordinate values) as the probe point. But system matrices (MA) are coming unstable, means eigen values of which are positive and negative both, which should come only negative. how to tackle this problem? Please tell what is creating the problem? I also want to know what is the feasibility of creating that domain probe point and why state space system matrix(MA) is coming Unstable?
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callback error

August 30, 2017, 4:29 am
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Hello,
did someone of you experience the following error message: "Internal error callback", at the end of the convergence process of a model?
What are possible causes of such a message and ways to fix the problem?
Thank you.
Massimo
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Boundary conditions vary a lot

August 30, 2017, 10:20 am
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Hello,

I got following problem:
I got a plate with a fixed temperature on the upper and on the lower side,
periodic boundary conditions on the sides
and heatflux boundary condition on the front and back.

Now the heatflux I put onto the model is a function or some other distribution I get from a file.
The problem now is that if I calculate the solution and look at the heat flux at the front and back, the output is nowhere near from what I assign as a boundary condition (Variation of various 100%).
So COMSOL is messing with my boundary conditions and changing the net influx, which I really do not like.

Are there any known fix to that? And why is Comsol doing that?
My boundary conditions are resolved very highly and my mesh is also not pretty fine.

Best,

Toby
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How to simulate a charge-discharge cycle into a tank?

August 30, 2017, 11:03 am
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Hello! I´m tryng to simulate a charge-discharge process into a tank, but a I dont know how to reverse the boundary conditions, for example, change the upper fluid flow that is entering in the tank (charge), for a lower fluid flow that enter in the tank after 3600 seconds (discharge), when charge process finish. How can you vary the boundary conditions whith time? Thank you very much!
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Regarding Domain Materials

August 31, 2017, 2:48 am
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Dear All,

I tried to create a geometry for real surface data (as avilable in .txt file) using parameteric surface and Interpolation function alraedy inbuilt in COMSOL. In real situation, whole data is NOT OF SAME MATERIAL, so I need to replicate the same in my comsol geometry.
But comsol assigns materials in domain only.
Is there any way, I can assign different materials for same domain?
If not so, is there any other solution for my probem?


--------------
Asha Sharma
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Adding electrical circuit in 3D geometry

August 31, 2017, 4:41 am
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Hello everyone. I am shamor. I am trying to simulate with AC/DC interface in comsol. I need to add some component to my geometry for my required result. For that I also have read "Inductor in an Amplifier Circuit" in detail. Although I have been facing some problem with geometry node and my Lt spice circuit node. From node A and B i want to measure potential difference given to my circuit diagram. Can anyone make it clear for me.
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Fluid Structure Interaction with Piezoelectric

August 8, 2012, 8:31 am
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I was wondering if someone could help me figure out how to model the fluid structure interaction using the piezoelectric device physics model as well. I am trying to model synthetic jet actuators and I am having a hard time coupling the physics together to make the model work. I am new to the fluid structure interaction model so that is probably where my issues are. I am able to get the piezo element to deflect but im not sure how to tie it to the brass element so that deflects and then that deflection causes the fluid in the cavity to displace. If anyone could help me that would be great.

Thanks,
Aaron
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Adding an extra dimension to 1-D battery model

March 16, 2016, 3:35 pm
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Hi all,
I am working on modeling and simulation of Li-ion battery. My model is pseudo-2-dimensional one. So I need an extra dimension to consider diffusion equation in solid phase of porous electrode in radial-direction while other equations are assumed in x-direction. I do not know how to do that. Please help me.
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