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How do I do a plot of total plate stress against frequency?

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I have a shell plate being driven by a point load and I already have surface stress plots that show stress at particular frequencies. What I'd like to do now is do a line graph showing total plate stress at each frequency - right across the frequency range (so total plate stress over frequency). Can anyone tell me how to do this?

Many thanks in advance

Step Function as BC

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I want to implement a change in the velocity/flow in a laminar flow problem. I added the step function (tag: step1) but I am wondering what the correct syntax is when adding this in the velocity boundary condition for the inlet condition to the laminar flow problem...ie: under Uo what exactly do I need to enter?

The step function parameters are: Location: 0.5, From: 0, To: 1
Goal: flow of 0.1m/s for the first 5 seconds then add 0.1m/s of flow from 5--> 10 seconds.

Convergence: when should I stop the model?

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Hi everyone

I have been working on models that take several days to solve. One of them is running at the moment, and I just have a general question.

When I look at the Convergence Plot 2, which is "Reciprocal of step size" vs "Time step", I can see the reciprocal of step size is between 10^5 and 10^6. It has been like this for several hours, and the progress value is at 2% without increasing.

I need results for this simulation by the beginning of next week. When do you know if you should stop the simulation or let it run and solve this convergence difficulty eventually? If I stop it, and the model could have advanced and solved, then I'll lose several hours of solving. But if I don't stop it, it might be at 2% for more than a day.

What should I do? What are the general guidelines on convergence?

Thank you so much!
Sylvana

How can I export an eps image (vector graphics)?

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Hello,

I would like to export an image of the model geometry as an .eps file (vector graphics). I could not find how to do that and it seems that the only options are jpg, png and bmp.

Thank you.

Surface evaporation, condensation

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Hi,

I want to model surface evaporation from a water flow at 40 Celsius and observe the consequent condensation on a cold surface. Can you help me with the model that I should use? I could not find anything similar in the online available models.

Thanks,
SMHH

New "Introduction to COMSOL Multiphysics" book now available

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Hello,

We are pleased to announce that a new version of the "Introduction to COMSOL Multiphysics" book is now available for immediate download at:
www.comsol.com/shared/download...uctionToCOMSOLMultiphysics.pdf

The highlights of this new version are:
- a brand new introduction chapter
- a thorough overview of the COMSOL Desktop
- updated models with step-by-step instructions
- new appendices about shortcuts, language elements and reserved names, file formats and LiveLink add-ons

Enjoy!
Valerio

Apparent inconsistency in induction heating solution methods

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Hi everyone,
I'm new to COMSOL 4.3, and I'm trying to properly use the induction heating module. While modeling the problem of a current loop heating several iron inductors embedded in water in 3D, using either External Current Density or Surface Current, I kept getting temperatures that I strongly suspected were too low. I modeled a similar problem of one inductor in axisymmetric 2D, with the intention of comparing heating via Single-Turn Coil Domain with heating from either of the aforementioned methods. I get a result that seems right to me with Single-Turn Coil Domain, but when I deactivate it and activate either External Current Density or Surface Current, I get a temperature rise of less than a degree, a similar wrong result to what I get with 3D modeling.
With External Current Density, I use the current (1000 A) divided by the cross-sectional area of the loop wire, and I use the current divided by the circumference of the loop wire when I use Surface Current instead.
I've attached the 2D axisymmetric version of the test problem that delivers incorrect results. I've slightly modified the materials such that water has a relative permittivity and permeability both of 1, and an electrical conductivity of 0.1 S/m. Can anyone let me know what I'm missing? Thanks in advance!

how can I use plasticity model in the poroelasticity module

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I want to use soil plasticity model in the poroelasticity module? How can I add soil plasticity model into the poroelasticity module? I notice I can add soil plasticity model in the structural mechanics module, but I can not find soil plasticity model in the poroelasticity module.
Thanks

Tutorial required

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Hi,

Does any one have a tutorial on coupling 3D SM module with 3D shell with continuity of displacement boundary condition at the interface???. How can it be done in Comsol 3.5(a).

Kindest regards

Help understanding detailed solver log and time-step size selection

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Hello Everyone,

Could someone please help me understand what is happening in this excerpt from one of my solver logs? I'm trying to understand what exactly the non-linear solver is 'thinking' so that I can understand why its failing to converge.

I'm using a fully coupled solver with automatic time-stepping. From my reading I've gathered that the automatic time-stepping attempts to estimate a timestep such that the error will be less than the prescribed tolerance. When it fails it should be taking shorter time-steps. However, in my log it appears to me that the solver is barely decreasing it's step size (0.019 to 0.0069) despite failing to converge numerous times. Why is this? I also notice that the damping does not always decrease despite not finding a solution.

I am missing a good deal of information about the detailed solver log. Can anyone direct me to a good source? Why is the stepsize not displayed in seconds? Is the stepsize the time-step before or after applying the damping? In automatic time-steping mode the Jacobian is supposed to be updated on each iteration. Why is the number of Jacobian evaluations less than half the number of solution evaluations?


Step Time Stepsize Res Jac Sol Order Tfail NLfail
81 6.6048e+006 65536 out 238 118 267 2 0 5

Time t = 6.6048e+006.
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.018 0.0093350 0.019 241 119 270
2 0.019 0.0164827 0.019 242 120 272
3 0.018 0.2523938 0.019 243 121 274
4 0.013 0.6283830 0.017 244 122 276
5 0.32 0.0013936 0.32 245 123 278
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0072 0.2885796 0.0097 248 124 281
2 0.01 0.2970095 0.012 249 125 283
3 0.015 0.0299090 0.015 251 126 286
4 0.15 0.0003656 0.15 252 127 288
5 0.69 0.0000205 0.69 253 128 290
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0077 0.1348999 0.0089 256 129 293
2 0.013 0.0343265 0.013 257 130 295
3 0.1 0.0005208 0.1 258 131 297
4 0.28 0.0000161 0.28 261 132 301
5 0.34 0.0000000 0.34 274 133 315
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.029 0.0020000 0.029 277 134 318
2 0.021 0.0060284 0.021 278 135 320
3 0.0026 0.0018224 0.0026 280 136 323
4 0.0036 0.0014934 0.0036 281 137 325
5 0.0047 0.0029224 0.0048 282 138 327
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0074 0.0020000 0.0074 285 139 330
2 0.0088 0.0018893 0.0088 286 140 332
3 0.0087 0.0161047 0.0089 287 141 334
4 0.0035 0.0015245 0.0035 289 142 337
5 0.0063 0.0006903 0.0064 290 143 339
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0066 0.0024182 0.0066 293 144 342
2 0.0084 0.0029417 0.0084 294 145 344
3 0.008 0.0244975 0.0083 295 146 346
4 0.037 0.0010122 0.037 296 147 348
5 0.34 0.0000000 0.34 305 148 358
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0066 0.0030088 0.0066 308 149 361
2 0.0086 0.0035414 0.0086 309 150 363
3 0.0076 0.0318030 0.008 310 151 365
4 0.079 0.0003457 0.079 311 152 367
5 0.2 0.0000335 0.2 313 153 370
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0067 0.0031310 0.0067 316 154 373
2 0.0088 0.0036122 0.0088 317 155 375
3 0.0077 0.0320992 0.0081 318 156 377
4 0.076 0.0003791 0.076 319 157 379
5 0.17 0.0000648 0.17 321 158 382
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0068 0.0031033 0.0068 324 159 385
2 0.0091 0.0034830 0.0091 325 160 387
3 0.008 0.0313162 0.0084 326 161 389
4 0.11 0.0001941 0.11 327 162 391
5 0.24 0.0000691 0.24 328 163 393
Iter ErrEst Damping Stepsize #Res #Jac #Sol
1 0.0069 0.0030643 0.0069 331 164 396
2 0.0093 0.0033734 0.0093 332 165 398
3 0.0082 0.0306668 0.0086 333 166 400
4 0.16 0.0000882 0.16 334 167 402
5 0.37 0.0000291 0.37 335 168 404

Step Time Stepsize Res Jac Sol Order Tfail NLfail
81 6.6048e+006 65536 out 335 168 404 2 0 15
Time-Dependent Solver 1 in Solver 1: Solution time: 756 s. (12 minutes, 36 seconds)


Thanks for your help guys,
Andrew

Is the Comsol Model Class a Handle Class in Matlab? Can/should I pass it as "call by reference"?

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Hey there,

I'm new to Comsol and I'm developing my first Matlab application using LiveLink. As I understand the object oriented concept in Matlab, there are two types of classes. Value Classes and Handle Classes. Instances of the latter can be used as function argument in the sense of "call by reference".

Which of those two types of Matlab classes belongs the Comsol Model Object to?
If I load a Comsol model in Matlab using the Matlab code

model = mphload(mymodel.mph, 'My Model');

can I then pass the above variable to some Matlab function "myFun()" as call by reference, modify in that function the Model Object and see the modifications in the main Matlab script when returning from "myFun()"?

Is that all save to do or what is the best practice to structure and modularize Matlab code when using the Comsol Model Object?

Thanks a lot in advance,
Joerg

unable to rectify the syntax error in expression

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sir,i have neen trying the example problem Electroosmotic Flow in Porous Media
Model ID: 11
after computing it says syntax error in expression. . .i could not rectify it. . so please give me a solution at the earliest

Spinning Disk Trick

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Hello guys!

My name is Domien and I'm new here :)
I'm a physics student at the University of Antwerp, Belgium. I'm currently working on my Bachelor's thesis.

I'm trying to model a Spinning Disk with a hole in it, just like in this fun video: www.youtube.com/watch?v=h0SZZTBQmEs
It is my goal to learn more about this weird effect by modeling the spinning disk in COMSOL. However, I am new to COMSOL and there is nobody at the University who can help me with it. That's why I'm asking you guys for help :)

I have already succeeded in modeling the disk itself and a rectangular cuboid, which serves as the floor. Things yet to be done: add gravity to the disk, add friction between the objects, make it a time-dependent study and set initial velocity and position.

Can any of you awesome people help me with this? :D

Thanks!

Domien

PS: When I'm at the University on monday, I will be able to upload my latest file.

electroosmotic flow in porous media. . . .pls friends respond me. . . .i am new to comsol

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it says expression syntax error while computing. . . plz work it out and help me how to rectify it. . . .its an example problem. . . .just type electroosmotic flow ih documentation help. . .u will find it in the first line. . . .plz solve and reply how you rectified the error. . . .friends help me to get out of that error

old model cannot be reconstructed....

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I am attempting to build on a model using Darcy's law to model solute transport under saturated conditions. The original model was built in COMSOL 3.5a, and I get an error message "Old model cannot be reconstructed. Do clear solution to expunge. File not found." Help.

Regarding Hand Tool in work plane

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Hello,

I am trying to design a complex and very minute pattern in micro-meter scale on a work plane but I am not able to figure out how to move the plane while working, I need to zoom in and out again and again to move it.

Is there any "Hand Tool" which I can use to move the plane?

Step function

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Very simple question, but I can't find out how to do it.

I have a external temperature, "Temperature 1", which is 100 C. After 330 seconds I would like it to drop 80 degrees to 20 degrees. I should be able to use a step funtion, but can't figure out how to. An easier approach is also very welcome. Thanks in advance!

Electromagnet modeling in 3D BH curve&relative permeability

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Hi all,
at start let me say I am new in Comsol. I am using v 4.0a AC/DC Magnetic Fields. What I am trying to model is type of a magnetic brake. It`s geometry is very similar to plain electromagnet, consisting out of single cylindrical coil and a single (or mere) solid cylindrical iron (or other materials) solenoid. I have successfully modeled this geometry, defined all parameters and got results in 3D Plot Group 2/Slice 1/Arrow Volume 1/ etc. See attachment.
The thing that troubles me is how to define VARIABLE RELATIVE PERMEABILITY as a B-H curve function. i have modeled this geometry entering a number in relative permeability field but that is not want I want. I want to enter a r. permeability as a B&H curve function for specific material. I have data for B-H curves for materials of interest. I tried to type mu0*(normB/normH) as a equation in material`s relative permeability field and Comsol accepted this but I still do not see how or where to define B-H curve.
The main reason for doing this, correct me if I am wrong, is that I think I should enter relative permeability as a function not as a fixed number in case if I decide to make a solenoid out of two very different materials.
I know I haven`t presented my situation as best as it should, but I think You get the picture.
So, to summarize, should I enter relative permeability for certain material as a fixed number of as a B-H curve function and if so, how to do it?
Thank You all.

about helix geometry modeling

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Hi, I am trying to model a spiraling geometry (helix-like) with a complicated cross section. Does anyone know how to do it with comsol 4.2/4.3a?

I used the build-in "helix" one but that was with a circle cross section while what I want is actally not that simple.

Thanks for any feedback!

3-D Modelling , Filling an open gap

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Good Afternoon,


I'm building a damper that has a hollow casing and a rubber-ish inside. This rubber is applied inside the case trough a direct injection.

I'd like to know if I can model the casing ( using Material 1 ) then fill the gap of the case with another material ( Material 2 ).


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