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Electromagnetic actuator

February 22, 2013, 3:19 am
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I have problem with coupling the magnetic that generated by 2D Coil with permanent magnate to actuate the cantilever beam. Also, I have faced problem to specify the boundary of moving mesh that is necessary to calculate the the displacement of cantilever. Also, the current flowing through the coil was set at zero, but the result still shows that there is a force of attraction between the permanent magnet and the coil, which is not suppose to be so. There should'nt have been any interacting forces between the coli and the magnet. However, I have attached my file.
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Induction heating 2D with magnetic flux concentrator (MFC)

February 22, 2013, 5:36 am
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Hi all,

I have some problem with an induction heating simulation which has a magnetic flux concentrator (a material with a really high relative permeability) in it.

As a result, the metal plate heat up more with a mur=1 for the MFC than a mur=1.27324e7, which is wrong.

Could someone can tell me if I did an error on my model or if I misunderstood something?

My model and results are attached.

Best regards,


Pat
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"Nonsymmetric matrix found" error and meshing

February 22, 2013, 6:58 am
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Hello,

1 - I'm simulating a Newtonian incompressible fluid flow in a porous medium (medium formed by 1000 solid grains). For a mesh of 124816 elements, the computation runs normally and I get results. But when I refine the mesh, I get the error message (Nonsymmetric matrix found) and solver stops working.
Do you have any idea of ​​the origin of this error?

2 - Can you please tell me how can I generate a structured mesh or a mesh of hexahedral elements for the geometry of the model here attached.

Thank you.

Mehrez Agnaou
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Induced current/voltage from one coil in another

February 22, 2013, 7:12 am
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Dear community,
I just started to use COMSOL. Now, I'm trying to model two cylindrical coils with different radius but at the same position (also same length and thickness). I'd like to apply a frequency dependent current on the inner one and simulate the induced voltage (and current) in the outer one. Now, I'm not sure how to model the outer coil. Do I have to connect it to a circuit or is there a way to use the multi-turn coil domain?

Thanks for your help and suggestions!
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Troubles with reading COMSOL text data files and files with interpolation functions

February 22, 2013, 7:50 am
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Hello everyone!

I have some troubles with creating my own reader for COMSOL text data files and files with interpolation functions. I have read "The COMSOL File Formats" section of COMSOLMultiphysicsReferenceGuide.pdf (for v4.3.a) but it didn't help.

Problem 1) In data files, for "Mesh" Serializable, there is a section where number of parameter values per element (NER), number of parameter sets (NR) and matrix of parameter values (PAR) are defined. Here are some questions:

a) In some files matrix has, as specified in ReferenceGuide, NER x NE values. But, in some cases I found (3 * NER) lines every with NR values. Is this correct?
b) Are these values per element or per node values?
c) Are these values scalar or vector values (perhaps what I found under a) is model with vector (3tuple) values)?

Problem 2) I need to display some values defined in separate file as interpolation functions (as I understood from ReferenceGuide) defined on cloud of points. These points from cloud approximately match with (not always strict) subset of mesh points from data file. Is there a way to connect points from data file with points from cloud in constant time (i.e. without using k-d tree and similar techniques)? I believe there is a way to connect them becase they approximately match, but I don't know how points from cloud are created. Do You have any idea?

Thank You for Your help!

Best regards,
Nenad.
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CAD data for KEMAR

February 22, 2013, 11:06 am
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Hello. I have seen papers with scans of the KEMAR manikin, such as from Mads Jensen when he was at Widex. I am in need of CAD data (e.g. STEP file) for the KEMAR head.

Does anyone have such data? Would they be willing to share it? I do not have my own laser so I can't measure it myself.

Thanx,
Jay
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calculating average element size

February 17, 2011, 3:29 pm
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Hi,

I am trying to characteise the effect of mesh quality and element size on the solution of a model. I have generated a standard and several refined meshes using an external software (Simpleware) and imported them to Comsol.

I am using q = meshqual(fem.mesh); to calculate the mesh quality.

Is there a similar command or calculate the average element size?

I have tried a subdomain plot of "h" the element size, exporting the plot data to Matlab and calculating the average. However I have noticed the number of elements in the output file is alot more than the real number of elements.

I am not sure how the export plot data works in this case? Is it exporting the element size at each vertex?

Thanks

Amr

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Heat Transfer in Soils

November 28, 2012, 9:55 am
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Hi,
I am a comsol user and I want to have a 2d axisymmetric model. In my model, I have a soil sample that I put a steel bar in the soil. I want to heat the steel bar with a constant temperature 500(k) and then wait for 6 hours to see that how the heat will be conducted in the soil. The problem that I have is that after simulation, I do not know why I could not have good results. The heat will just be conducted at the top of the model, and the rest of the model will remain unaffected. You can see my model in attached file.So if it possible, I want to know that what do I need to do to solve this problem? Where is my mistake?

Regards,
Al
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2D hinge in compliant mechanism

February 21, 2013, 8:21 am
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Hi all,

I am trying to simulate a compliant mechanism as seen in the attached picture but I am having difficulties simulating the rotating pin in 2D. As see in the picture the structure is composed of a flexing member and two rigid members connected by a pin. I made the geometry into an assembly instead of a union, the rotating pins as rigid connectors and the rigid bars as rigid domains. My question is how to model this rotating pin, I saw an example in 3D but I am not sure how to do this in 2D. Let me know what you guys think, I appreciate your help.


Thanks

Oscar

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Not able to properly use remesh feature in multiphysics stationary simulation

February 21, 2013, 10:50 am
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Hi,

I have simulated a steel specimen that becomes deformed due to bending. For that, I use the solid mechanics interface in a stationary study. Parametrizing the magnitude of bending also works. Overall, it works as expected.

I have also simulated an electromagnet by using the magnetic fields interface and specifying a DC external current density in a stationary study. That also works well.

I have attempted to include both of them in the same model, where I want the specimen to be deformed, remeshed, and that new mesh be used in the magnetic fields stationary study. Oh, and I want to parametrize the magnitude of bending, such that the sequence of operations is:

1. Deform 1 mm relative to rest position (calculate from initial mesh)
2. Remesh
3. Calculate DC magnetic fields (using remeshed geometry )

4. Deform 2 mm relative to rest position (calculate from initial mesh)
5. Remesh
6. Calculate DC magnetic fields using remeshed geometry

and so on...

So far, I have managed to remesh by using ALE and the model works without errors. However, I have a hunch that the magnetic fields interface only takes into account the initial mesh. As a result, the magnetic field distribution remains the same, and the only reason why it follows the shape of the deformed specimen in the plot, is because I have added "Deformation" as an addition to the plot. Could this be the case, what do you think?

I have been struggling with this for quite a while. Any ideas/suggestions would be highly appreciated. Thanks in advance for your time,

Kind Regards,
Orfeas
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Electrodeposition of chrome

February 22, 2013, 5:26 pm
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Hello,

We are trying to model a chrome plating process with a non-dissolving (inert) anode. We used the Tertiary, Nernst-Planck module with a moving mesh. We set up the electrodes as "External Depositing Electrodes", one for each of the cathode and anode. We are having trouble setting up an appropriate solver. At the moment, the solver uses two steps: (1) Current Distribution Initialization and (2) Time-Dependent Solver. For the first step, we are not able to achieve convergence with as many as 100 iterations. We have it set to a PARADISO solver. The messages on the log read as follows:

Nonlinear Solver
Number of degrees of freedom solved for: 28577
Nonsymmetric matrix found

and then it shows the results for the iterations.

We are also having trouble with the second step, where it keeps saying that the mesh is inverted, and thus, it does not proceed any further.

Any suggestions for which solver we should be using? Has anyone attempted a similar plating process?
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Error in Jacobian

February 22, 2013, 8:50 pm
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Can I know what the error means??

"Failed to find consistent initial values.
Segregated group 1

Failed to evaluate operator Jacobian.
Operator: nif, Geometry: 1, Boundary: 12 13 14 15 17 18 19 20 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 81 82 85 86 87 88 90 91 92 93 95 96 97 98 100 101 102 103 105 106 107 108 110 111 112 113 115 116 117 118 120 121 122 123 125 126 127 128 130 131 132 133 135 136 137 138 140 141 142 143 145 146 147 148 150 151 152 153 155 156 157 158 160 161 163 164 166 167 169 170 172 173 174 175 177 178 179 180 182 183 184 185 187 188 189 190 192 193 194 195 197 198 199 200 202 203 204 205 207 208 209 210 212 213 214 215 217 218 219 220 222 223 224 225 227 228 229 230 232 233 234 235 237 238 239 240 242 243 244 245
Last time step is not converged."
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Boundary condition at interface of two different materials in structural analysis module

February 22, 2013, 9:35 pm
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Hi,

I am trying to simulate a structural mechanics problem that utilizes 3D solid stress-strain module. I have a square plate of elastomeric material having a thikness in micro meteres and on top of this elastomeric substrate I have a metalic pattern having length in cm and thickness and width in micro meters. I want to know what B.C I should use on the interconnect face that is directly in contact with the surface of the substrate. Actually there are two options free and fixed since there are no continuity conditions on interfacial boundaries in structural mechanics module.

I shall be obliged if any one can give some guidance over this issue.

Thanks
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Changing License

February 22, 2013, 11:00 pm
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I wish to change the license of my COMSOL software from my institute's "Floating License" to "Trisl Version". Can I know how to do??
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Function as parameter.

February 22, 2013, 11:48 pm
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Hello

It is possible to use a function as a parameter in the geometry.
For example, replace the radius of the circle function of time.

Thank you.
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state space

February 23, 2013, 9:03 am
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Hi,

when we use mphstate to export state-space model, can we know the physical meaning of each states? Any help is appreciated.

Thanks
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Time to Reach Steady State in a Diffusion Problem

February 23, 2013, 9:55 am
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Hello,
Is someone able to help me, please?
I'm using COMSOL to model a diffusion problem. I have solved it using the stationary solver. I am able to see that at steady state the concentration on the far edge is 0.025 mols, by clicking on the image and viewing the results tab.
Is there a better (more automated) way to get this value?

I would also like to know the time to reach steady state - the definition of steady state I have chosen is 95% of the concentration when solved using the stationary solver. How would I find that? So far I have used the time dependent solver, and laboriously clicked through each time point, judging when the concentration reaches 95% using the results tab.
I'm certain there must be a better way of doing this, but I'm unable to find the answer in the forum. Hope someone can help, thanks in advance.
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Multicomponent multiphase flow

October 10, 2012, 3:52 am
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I am currently simulating a model in which the two carrier phases involved are water and toluene and the diffusing components are acetone and methyl isopropyl ketone (MIPK). This problem is to be solved using the Stefan-Maxwell equations together with the Navier-Stokes equations.

I have the inlet composition and the velocity conditions. I am in a fix as to which model is to be used for this. I have used the pde mode general form for Stefan-Maxwell equations and single phase Incompressible flow model for Navier-Stokes (each phase). I am attaching the model herewith. I am getting some results, but when I change the channel dimensions, the profiles of concentration and velocity do not change.
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Problems with sweep mesh

February 17, 2013, 7:28 pm
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Hi,

I have been trying to sweep mesh a domain (3-D). It will be like a small straight tube of rectangular cross section and having turns at right angles (like a serpentine). I tried to mesh the source and destination faces using 'edge' and 'mapped' option and subsequently tried to sweep mesh the entire domain. All I can get is, "invalid topology at the vertex". I found a pdf (lnf.umich.edu/nnin-at-michigan...loads/2012/11/comsol-guide.pdf), in which a domain similar to mine has been sweep meshed in page number 356 using comsol 3.5a. I am not able to find options like that in comsol 4.2, which I am using.

I kindly ask the experts in this area to comment on this and advice me. Thanks in advance.
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Imported SolidWorks part doesn't behave correctly

February 17, 2013, 7:31 pm
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I'm relatively new to COMSOL but I haven't had much luck finding a solution.
I had an assembly in SolidWorks made of 3 parts. I created a new SolidWorks part file which had the 3 parts mated together correctly and saved it. I imported that SolidWorks part into COMSOL. COMSOL recognized it as having 3 domains which I assigned different material properties to. I fixed the bottom and applied a load on the top. When I ran a tetrahedral static solid model test, the stress was what I expected for the top layer but it appears that it did not make it to the remaining layers. The stress on one side of the interface is a magnitude different than the other side, right at the interface. I attached a picture of this.

The nodes seem to align at the interface too. Even when I used the same mesh size for the entire model, I had the same issue. Does anyone have suggestions on a solution? I also attached my setup.
I can provide more detail and pictures if needed.

Thanks,
Jeremy
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