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Convergence problem with system of pde's: compressible flow + pde for density

March 21, 2014, 11:08 am
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Hi,

Here is the problem:
I am solving these equations having a periodic boundary conditions in a square. At the top and bottom of the square the constant velocity v0 and pressure p0 is applied. It is a very classical problem in fluid mechanics to learn about dynamic viscosity. Something new that is added, is another PDE to minimize the shear with changing the density value throughout the domain.
I am using the General Form toolbox, using the quadratic interpolation for velocity field, and linear for pressure and density, also the average of density should remain constant which I added a pointwise constraint. For meshing I used boundary layers top and bottom which the laminar flow toolbox uses (as far as I understood). The viscosity is a function of density and pressure so it makes it more non-linear. Something else about the the pde for density is that, it is highly non-linear in the term lambda.

It would be great if someone could give me some hints on improving the convergence. the g2 and g3 are laminar flow equations and the g4 is

2pρf'〖 γ〗^2-λρ=∇.(pv)

where λ is constant and γ is a function of velocity field.
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Error simulating fluid flow through microsieve

March 23, 2014, 7:32 am
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Hi everyone,
I'm newbie to COMSOL Multiphysics.
I'm trying to anticipate when a microsieve is broken under fluid flow (blood filtering), but some errors keep occuring.
Please help me!
Thanks very much!

[File]
drive.google.com/file/d/0B15nm...JZSnZodWtEMFU/edit?usp=sharing

[Error]
Failed to find a solution.
Segregated group 1

Singular matrix.

There are 1 void equations (empty rows in matrix) for the variable mod1.fsi.Pmfinl1.
at coordinates: (0,0,0), ...
and similarly for the degrees of freedom (empty columns in matrix).
Returned solution is not converged.
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one step vs. parametric sweep convergence

March 24, 2014, 3:01 am
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Good morning,

My solid mechanics model is basically a needle (modeled as a 3D solid not a beam) which is fixed at one side and laying over a box at the other side.

When the box is moved upward the needle is expected to bend. When the displacement (i.e. 3mm) is imposed in one step the box passes through the needle. However if the displacement is defined by means of a parametric sweep (i.e. 1mm, 2mm, 3mm) the model works and the needle bends.

Can anybody explain me that?
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Help with "Nonlinear solver did not converge"

March 24, 2014, 3:55 am
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Good day everyone!

I am working on a multiphysics problem involving reaction engineering, thermal stress, fluid flow in porous media, and species transport in porous media. At a certain timestep, I receive the error:
"
Nonlinear solver did not converge.
Maximum number of iterations reached.
Time: [max time solved for]
Last time step is not converged.
"
I am using a fully coupled (advanced, direct) solver for now, as I haven't been able to get a segregated solver to converge for even the first time step. My question is this: Is there any way I can go into the log files and find out which of my dependent variables is causing the convergence problem?

Thank you all!

-Nathan
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I have two models, model 1 and model 2. When solving model 2, the initial value of model 2 is the result of model 1. should I set it ?

March 24, 2014, 4:03 am
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I have a question. I have two models, model 1 and model 2. When solving model 2, the initial value of model 2 is the result of model 1. should I set it ? special information as follows:
(1) Model 1 and model 2 are same, include: exciting coil, pick-up coil and ferromagnetic pipe. Exciting coil is used to load current, pick-up coil is used to receive inducted voltage. Pipe is nonlinear. when current is in different stages, the B-H curve of pipe is different.

(2) The loaded current is shown in fig.1. When the time is 0-5 ms(denote as t1), the current ascends(I1), when the time is 5ms-50 ms(denote as t2), the current descends(I2).

fig.1
(3) The B-H curve of pipe is different. when the time is t1, the B-H curve ascends (BH1) , when the time is t2, the B-H curve descends (BH2) .

(4) Two models and two solvers. in materials, the B-H curves is different. They are shown in fig.2.

fig. 2
(5) The setting of solver 1 is the fig. 3: (a) is the step1: calculating coil current. (b) is the step2: calculating coil current 2. (c) is the step3: transient. The values of dependent variables are not to be chose.

fig. 3 (a)

fig. 3 (b)

fig. 3 (c)
(6) The setting of solver 2 is the fig. 4: (a) is the step1: calculating coil current. (b) is the step2: calculating coil current 2. (c) is the step3: transient. The values of dependent variables are to be chose in fig.4.(a), (b), (c). I hope the initial values of solver2 is the result of solver1.

fig. 4 (a)

fig. 4 (b)

fig. 4 (c)
(7) Induced voltage curve of solver 1 is shown in fig. 5. It is right. The induced voltage curve of solver 2 is shown in fig. 6(a), the fig. 6(b) is the enlarged view. However, the results are all zero. It is wrong. Why the results are zero?

fig. 5

fig. 6 (a) and (b)


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failed to find a solution when coupling heat transfer with fluids dynamic!!

March 24, 2014, 9:01 am
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Hi everyone

I'm trying to model a transformer using multiphysic (thermal, fluid dynamic) modeling on Comsol.
when using only the thermal modeling, (only using heat transfer physics)
the program is running.but when adding the Fluid to couple the two phenomenon (using non isothermal flow) i got a divergence error
Failed to find a solution.
Maximum number of Newton iterations reached.
Returned solution has not converged.
Any ideas? Attached you will find my model. Thanks.
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Frequency Dependent Permitivity.

March 24, 2014, 3:55 pm
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HI Comsol Users

I am trying to model the e-filed lines expected for a PbTiO3 crystal with electrodes on top and bottom to which I apply a voltage to the top one and leave the bottom one grounded.. I can easily get a surface plot of electric potential and from that show the e-field lines for what would effectively be a DC supply.

My problem arises when I then sweep it over frequency as nothing actually changes. I know it must have something to do with my PbTiO3 substrate having a frequency dependent permittivity however I am completely clueless as to how to programme this into COMSOL.

Also once I get this I was hoping I would also be able to model the leakage current across the crystal.

Any help would be appreciated.
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3D SPF Convergence Issues

March 24, 2014, 7:43 pm
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Hello,

I'm working on a 3D model in an attempt to simulate water waves in a tank generated by a sinusoidal pressure source. I've been able to create an otherwise equivalent 2D model which works, and have since then translated it into a 3D model, which doesn't always work. The 3D model works properly for low frequency and low amplitude pressure inputs, but beyond about 20 Hz, it fails. This suggested to me that I should increase the resolution of the mesh, though this did not appear to resolve my problem and significantly increases memory usage. I was able to avoid using too much memory by switching to a mapped mesh and using an iterative solver, though my model still didn't converge.

So I was hoping that someone here would be able to look at my model and make suggestions as to how I could improve it. I have uploaded two iterations of the model here: drive.google.com/file/d/0B2i7B...YyaFpSUVVCREU/edit?usp=sharing
cap3d_ale_40Hz_20Pa.diverge.mph is a model which I have most recently been working on, and still doesn't work.
drive.google.com/file/d/0B2i7B...ZQSmZvUVI0VTA/edit?usp=sharing
cap3d_ale.mph is the model I initially made which works at low frequencies and pressures.
Finally, I have linked a working 2D model:
drive.google.com/file/d/0B2i7B...x1bnFfNkN5SjA/edit?usp=sharing
Any suggestions would be appreciated!


Thanks,
Michael Deakin
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Extremely high local stress maxima in static analyses

March 25, 2014, 4:11 am
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Hi,

i'm experiencing a problem with a quite simple static analysis in comsol multiphysics.

In attachement 1 you can see the geometry of the model, which consists of two plates (aluminium) that are only connected in the circular areas.

In attachement 2+3 the mesh and the mesh statistics are shown, which are quite ok. A finer mesh is not possible, because of limitations in computational power. The mesh is a free tetrahedral mesh for the whole geometry.

loads and boundaries:
*Prescribed Displacement (x) of 0.005mm at the end of each plate (opposed directions)
*Prescribed displacement of 0mm in y and z direction at the end of each plate
*Symmetry (y-Directions)
*Continuity in each circular area

Solver:
MUMPS Solver with standard settings. Have tried PARDISO, which makes no difference to the result, but is a bit faster.

Results:
The deformation plot (Attachement 4) looks plausible. The stress plot (Attachement 5) shows circular stress distributions araound every contact area, which is also plausible, but it also shows very high, randomly distributed maxima around the contact areas which is not plausible for me.

Are there any ideas how to solve this problem? It seems to be a problem with the mesh, but it happened with different mesh sizes and parameters too.

Thanks for your help!
(The MPH File is in Attachement 6, if someone wants to take a closer look)
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Moving mesh plus automatic remeshing

March 25, 2014, 8:17 am
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Hi,
I want to simulate a cavity that moves into a solid with a specified velocity in a transient simulation. When the mesh quality becomes too low, I want to use the automatic remeshing feature. Depending on the initial mesh density and the chosen geometry shape order, I get one of the error messages during the simulation after some time steps:
#1: "condition for remeshing still fulfilled" or
#2: "self-intersections not supported"

Can anyone provide a hint how to avoid these errors? Please see the model file attached (vers. 4.4).

Best regards,
Marcel
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Coupling problem: Nernst-Planck equation with Poisson not converging

March 25, 2014, 8:43 am
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Hi,

I am unsuccessfully trying to implement to Poisson equation through the Electrostatic Module into the Module "Transport of Diluted species" for a stationary case.
Beside those modules I use the laminar flow module to account for the fluidics.
The model is supposed to describe a biochemical cell, with a fixed ion concentration streaming into a reaction chamber onto a sensor. The variable of interest would be the resulting ion concentrations for both species. On that sensor species of one kind are transported out of the model, accounted for with the "flux" boundary condition.
I activated both migration through the Electrical field and convection through the fluid in the ion transport module.
As I understand the Electrical field created by the ion species are not automatically accounted for by these modules, so I created a space charge density as with z the respective ion charges and c the respective ion concentrations.
Without the space-charge density everything converges fine, with the space charge density implemented however, the solution does not converge. I tried different solver combinations, first solving for the fluidics, finer grid resolution and no steep gradients, but without any success.
Does anybody have any experience in coupling Poisson with NP? I'm starting to think some of the boundary conditions are not set up correctly...
It would be awesome if anybody could have a look at my model.

Thanks a lot,

Raphael

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Error message: Failed to evaluate expression. Failed to evaluate operator. Failed to evaluate variable.

May 17, 2011, 3:08 am
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Hi people

I have been encountering this error message:

Failed to evaluate expression.
- Expression: d(d((-(mod1.chds.nx*mod1.chds.u+mod1.chds.ny*mod1.chds.v+mod1.chds.nz*mod1.chds.w)*mod1.c*test(mod1.c))*(dvol),{test@1}),mod1.c)
Failed to evaluate operator.
- Operator: mean
- Geometry: 1
- Boundary: 42 81 82

I have been working around with boundary conditions, initial values suchlike, but I am not sure if I am on the right track because I either receive the error message above or this error message:

Failed to evaluate expression.
- Expression: mod1.p-mod1.dl.p0
Failed to evaluate variable.
- Variable: mod1.dl.p0
- Defined as: (g const*(mod1.dl.H0*mod1.dl.rho))
Failed to evaluate operator.
- Operator: mean
- Geometry: 1
- Boundary: 42 81 82 83

Why are all these error messages?

Thanks in advanced!

regards
Liwah
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comsol error Failed to evaluate variable.

June 26, 2011, 8:14 am
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I have this error, see the attached file.

Can any one help me quickly, please ?

Thanks.
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cluster computing

March 6, 2013, 9:31 am
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Hello,

Can anyone help me figure out these errors andor how to run a very large model on multiple nodes?

I am having a terrible time trying to run a very large model on multiple nodes on our cluster. I know that it can work, because I have successfully run smaller models on multiple nodes. But now, I have a very large model, due to a very fine mesh, that will not run successfully. I keep getting memory errors, its as if COMSOL does not have enough memory, but it also looks like COMSOL may not be utilizing all of the cores on each node. I cannot attached the log file, because it is not a .mph file, but I have copy and pasted all of the information below.
I would be so grateful for any insight,
Kelley


12 bn124
12 bn120
12 bn119
12 bn118
running mpdallexit on bn124
LAUNCHED mpd on bn124 via
RUNNING: mpd on bn124
LAUNCHED mpd on bn120 via bn124
LAUNCHED mpd on bn119 via bn124
LAUNCHED mpd on bn118 via bn124
RUNNING: mpd on bn120
RUNNING: mpd on bn118
RUNNING: mpd on bn119
bn124
bn119
bn118
bn120
Warning: The number of allocated threads (48) exceeds the number of available physical cores (12)
Warning: The number of allocated threads (48) exceeds the number of available physical cores (12)
Warning: The number of allocated threads (48) exceeds the number of available physical cores (12)
Warning: The number of allocated threads (48) exceeds the number of available physical cores (12)
[0] MPI startup(): cannot open dynamic library libdat2.so.2
[0] MPI startup(): cannot open dynamic library libdat2.so
[0] MPI startup(): cannot open dynamic library libdat.so.1
[0] MPI startup(): cannot open dynamic library libdat.so
[2] MPI startup(): cannot open dynamic library libdat2.so.2
[2] MPI startup(): cannot open dynamic library libdat2.so
[2] MPI startup(): cannot open dynamic library libdat.so.1
[2] MPI startup(): cannot open dynamic library libdat.so
[3] MPI startup(): cannot open dynamic library libdat2.so.2
[3] MPI startup(): cannot open dynamic library libdat2.so
[3] MPI startup(): cannot open dynamic library libdat.so.1
[3] MPI startup(): cannot open dynamic library libdat.so
[1] MPI startup(): cannot open dynamic library libdat2.so.2
[1] MPI startup(): cannot open dynamic library libdat2.so
[1] MPI startup(): cannot open dynamic library libdat.so.1
[1] MPI startup(): cannot open dynamic library libdat.so
[0] MPI startup(): tcp data transfer mode
[1] MPI startup(): tcp data transfer mode
[2] MPI startup(): tcp data transfer mode
[3] MPI startup(): tcp data transfer mode
[0] MPI startup(): Rank Pid Node name Pin cpu
[0] MPI startup(): 0 11779 cn172 {0,1,2,3,4,5,6,7,8,9,10,11}
[0] MPI startup(): 1 27813 cn168 {0,1,2,3,4,5,6,7,8,9,10,11}
[0] MPI startup(): 2 10950 cn167 {0,1,2,3,4,5,6,7,8,9,10,11}
[0] MPI startup(): 3 17204 cn166 {0,1,2,3,4,5,6,7,8,9,10,11}
Node 0 is running on host: cn172
Node 0 has address: cn172
Node 1 is running on host: cn168
Node 1 has address: cn168
Node 2 is running on host: cn167
Node 2 has address: cn167
Node 3 is running on host: cn166
Node 3 has address: cn166
Warning: The total number of allocated threads (48) on host: cn168 exceeds the number of available physical cores (12)
Warning: The total number of allocated threads (48) on host: cn172 exceeds the number of available physical cores (12)
Warning: The total number of allocated threads (48) on host: cn167 exceeds the number of available physical cores (12)
Warning: The total number of allocated threads (48) on host: cn166 exceeds the number of available physical cores (12)
COMSOL 4.3a (Build: 161) starting in batch mode
*******************************************
***COMSOL 4.3.1.161 progress output file***
*******************************************
Tue Mar 05 16:35:19 PST 2013
Opening: /ibrix/home16/rabjohns/rundir/2.28mesh.025.mph
Open time: 12 s.
Running: Study 1
Number of vertex elements: 4
Number of edge elements: 400
Number of boundary elements: 10000
---------- Current Progress: 100 %
Memory: 563/563 8291/8291
Node 1:
Number of vertex elements: 4
Number of edge elements: 400
Number of boundary elements: 10000
Node 2:
Number of vertex elements: 4
Number of edge elements: 400
Number of boundary elements: 10000
Node 3:
Number of vertex elements: 4
Number of edge elements: 400
Number of boundary elements: 10000
----- Current Progress: 55 %
Memory: 575/575 8291/8291
------- Current Progress: 75 %
Memory: 604/604 8291/8291
Number of vertex elements: 8
Number of edge elements: 936
Number of boundary elements: 33600
Number of elements: 340000
---------- Current Progress: 100 %
Memory: 629/629 8355/8355
Minimum element quality: 1
Node 1:
Number of vertex elements: 8
Number of edge elements: 936
Number of boundary elements: 33600
Number of elements: 340000
Minimum element quality: 1
Node 2:
Number of vertex elements: 8
Number of edge elements: 936
Number of boundary elements: 33600
Number of elements: 340000
Minimum element quality: 1
Node 3:
Number of vertex elements: 8
Number of edge elements: 936
Number of boundary elements: 33600
Number of elements: 340000
Minimum element quality: 1
Current Progress: 0 %
Memory: 663/663 8355/8355
Memory: 900/900 8622/8622
---------- Current Progress: 100 %
Memory: 937/937 8610/8622
Time-Dependent Solver 1 in Solver 1 started at 5-Mar-2013 16:36:04.
Time-dependent solver (BDF)
Current Progress: 0 %
Memory: 1456/1456 9131/9131
Memory: 1520/1520 9195/9195
Warning: PARDISO is not distributed. Switching to MUMPS.
Memory: 2860/2860 10513/10513
Warning: PARDISO is not distributed. Switching to MUMPS.
Memory: 20575/20575 27794/27794
Memory: 22470/22470 30011/30011
Number of degrees of freedom solved for: 16726014.
Memory: 29744/29744 37274/37274
Memory: 35766/35766 43219/43219
Nonsymmetric matrix found.
Scales for dependent variables:
mod1.u: 9.2e-05
mod1.p: 1
Symmetric matrices found.
Format not changed since SOR line uses nonsymmetric storage.
Scales for dependent variables:
mod1.bc: 0.05
mod1.ac: 0.05
Memory: 43291/43291 50752/50752
Nonsymmetric matrix found.
Step Time Stepsize Res Jac Sol Order Tfail NLfail LinIt LinErr LinRes
Memory: 20186/43291 51079/51079
Memory: 35272/43291 83099/83099
Memory: 37667/43291 84978/84978
Memory: 38350/43291 85705/85705
Memory: 43061/43291 105054/105054
Memory: 47498/47498 111297/111297
Memory: 57658/57658 115600/115600
Memory: 59547/59547 117720/117720
Memory: 59832/59832 118281/118281
Memory: 61138/61138 116498/118281
Memory: 62323/62323 117852/118281
Memory: 64075/64075 119805/119805
Memory: 65421/65421 128049/128049
0 0 out 20 22 0 0
Group #1: 20 21 0
Group #2: 0 1 0 0 6.9e-310 6.9e-310
---------- Current Progress: 100 %
Memory: 19786/65421 27342/128049
Node 1:
Time-dependent solver (BDF)
Warning: PARDISO is not distributed. Switching to MUMPS.
Warning: PARDISO is not distributed. Switching to MUMPS.
Number of degrees of freedom solved for: 16726014.
Nonsymmetric matrix found.
Scales for dependent variables:
mod1.u: 9.2e-05
mod1.p: 1
Symmetric matrices found.
Format not changed since SOR line uses nonsymmetric storage.
Scales for dependent variables:
mod1.bc: 0.05
mod1.ac: 0.05
Nonsymmetric matrix found.
Step Time Stepsize Res Jac Sol Order Tfail NLfail LinIt LinErr LinRes
0 0 out 20 22 0 0
Group #1: 20 21 0
Group #2: 0 1 0 0 6.9e-310 6.9e-310
Node 2:
Time-dependent solver (BDF)
Warning: PARDISO is not distributed. Switching to MUMPS.
Warning: PARDISO is not distributed. Switching to MUMPS.
Number of degrees of freedom solved for: 16726014.
Nonsymmetric matrix found.
Scales for dependent variables:
mod1.u: 9.2e-05
mod1.p: 1
Symmetric matrices found.
Format not changed since SOR line uses nonsymmetric storage.
Scales for dependent variables:
mod1.bc: 0.05
mod1.ac: 0.05
Nonsymmetric matrix found.
Step Time Stepsize Res Jac Sol Order Tfail NLfail LinIt LinErr LinRes
0 0 out 20 22 0 0
Group #1: 20 21 0
Group #2: 0 1 0 0 3.2e-322 1.3e-311
Node 3:
Time-dependent solver (BDF)
Warning: PARDISO is not distributed. Switching to MUMPS.
Warning: PARDISO is not distributed. Switching to MUMPS.
Number of degrees of freedom solved for: 16726014.
Nonsymmetric matrix found.
Scales for dependent variables:
mod1.u: 9.2e-05
mod1.p: 1
Symmetric matrices found.
Format not changed since SOR line uses nonsymmetric storage.
Scales for dependent variables:
mod1.bc: 0.05
mod1.ac: 0.05
Nonsymmetric matrix found.
Step Time Stepsize Res Jac Sol Order Tfail NLfail LinIt LinErr LinRes
0 0 out 20 22 0 0
Group #1: 20 21 0
Group #2: 0 1 0 0 1.8e-322 6.3e-322
Time-Dependent Solver 1 in Solver 1: Solution time: 16046 s. (4 hours, 27 minutes, 26 seconds)
Exception:
com.comsol.util.exceptions.FlException: Failed to find consistent initial values
(rethrown as com.comsol.util.exceptions.FlException)
Messages:
The following feature has encountered a problem

Failed to find consistent initial values

Segregated group X#1



Out of memory LU factorization

Last time step is not converged
- Feature: Time-Dependent Solver 1 (sol1/t1)
- Error: Failed to find consistent initial values.
- Error on node 1: Failed_to_find_consistent_initial_values
- Error on node 2: Failed_to_find_consistent_initial_values
- Error on node 3: Failed_to_find_consistent_initial_values

Stack trace:
at com.comsol.solver.SolverOperation.addError(Unknown Source)
at com.comsol.solver.SolverOperation.execute(Unknown Source)
at com.comsol.model.internal.impl.SolverSequenceImpl.a(Unknown Source)
at com.comsol.model.internal.impl.SolverSequenceImpl.g(Unknown Source)
at com.comsol.model.internal.impl.SolverSequenceImpl$an.a(Unknown Source)
at com.comsol.model.internal.impl.SolverSequenceImpl$an.execute(Unknown Source)
at com.comsol.model.clientserver.ClientManagerImpl$d.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: Exception:
com.comsol.util.exceptions.FlException: Failed to find consistent initial values
Messages:
Failed to find consistent initial values

Segregated group X#1



Out of memory LU factorization

Last time step is not converged

... 11 more
Saving: /ibrix/home16/rabjohns/rundir/2.28mesh.025_out.mph
Save time: 51 s.
Total time: 16142 s.
--- Job finished at: Tue Mar 5 21:04:28 PST 2013
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baffled duct - PML 3D PROBLEM

March 25, 2014, 4:47 pm
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Hello every one,
I’d like to excite a cylindrical waveguide (rigid in one face and flanged in the other one) with a monopole located in M(x,y,z) and compute the pressure inside the duct. Also, compute the far field radiation within comsol 3D.
I used Comsol to validate my analytical code in the case of a cylindrical duct with different boundary conditions. The results are perfect unless all the walls are hard except the outlet which is flanged (=I use the radiation impedance formulation of a baffled piston in terms of struve and bessel functions). To model the infinite baffle, I employed 2 PMLs . The first one has the same radius of the main duct. The second with a bigger radius (I obtained sound pressure level results as shown in the attached screen shot 1.5 a , 2a, 5a) .Please find herewith the model as well (with PLM 2 Radius = 1.5a) . I applied five elements in the swept direction in the PMLs ( the PML scaling factor is 1).

Could you please let me know how to adapt the 3D PMLs to the problem inorder to get better results ?

Best regards.

Aniss
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Search

Solver Configuration for Nonlinear Highly Coupled Fluid Flow Chemical Reaction Model

March 25, 2014, 8:44 pm
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Good Evening,

I've been working with Comsol for the last four months trying to model a system using the Free and Porous Media Flow module coupled with the Concentrated Species module (along with the Heat Transfer and poisson equations for electrical potential however those are currently not of concern and assumed to be disabled or constants ie. T=const).

The two primary modules above converge nicely without the addition of chemical reactions however once chemical reactions are added into the flowfield and porous media it is unable to converge. I have tried making the mesh finer,inner parametric steps, segregated solver and many configurations for iterative solvers however I am unable to attain convergence. If someone could take a look that would be great.

Thanks,
Melissa
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Work on COMSOL through MATLAB?

May 3, 2011, 3:36 am
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Hi,

I would like to run COMSOL through MATLAB but don't understand how? For example when I have saved a COMSOL simulation as M-file and tries to open it in MATLAB it won't open and I am not sure how to open the program in COMSOL in MATLAB. I tried to read the information in help but I don't get it. I didn't install the programs on this computer so I am not sure how it was installed.

Basically my end goal is that I want to save the solutions from COMSOL in MATLAB to be able to use them for further calculations in MATLAB. Is it possible and how can I do this?

For example, I have a certain parameter (a refractive index as input) that I sweep and get different effective refractive indexes. I would like to store these in MATLAB and then use it for calculations in MATLAB. How can I do this?

Edit:

I have MATLAB R2010B 64BIT, COMSOL4.1, MATLAB was installed first. I uses a Mac computer.

Many thanks for any help!
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Problem in one of the Model Library of Comsol 3.5

March 26, 2014, 10:32 pm
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Hey guys,

I'm currently trying the model 'Two Phase Fluid-Structure Interaction' in V3.5's Model Library. You can find this at Model Library-> MEMS Module-> Microfluidics Models->twophase fsi. An animation is also available.

There is one problem however. When I'm following the instructions in 'Modeling Using the Graphical User Interface' step by step, an error message appears as following:
Error:
Failed to find consistent initial values.
Undefined_value_found_Linsolv
NaN_or_Inf_found_when_solving_linear_system_using_PARDISO
And I just cannot figure out why. Could someone help me find it out?

Thank you in advance!
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Parametric Sweeping a Geometrical Parameter! Possible?

March 27, 2014, 9:34 am
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I have a polymer coil in a solid cylinder. This is a reaction-diffusion model. I think usually the materials property or other similar non-geometrical properties are sweeped in parameter sweep.

I want to vary the coil's diameter in parameter sweep. Is this possible? Whats the protocol for meshing for doing this?
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problem in comsol program

March 28, 2014, 1:01 am
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Hi comsolers,

I defined two projects in comsol in 2D for solving richards equation:
first project: simple rectangle that left boundary was defined as pressure head=0.8 and right boundary as pressure head=0.5, the other two angles= zero flux
and then I made a cross section from these two points from 0.8 to 0.5 (attached cross section as picture1).

Second project: simple rectangle that left boundary was defined as step function for the pressure head from zero to 0.8 =0.8 and from 0.8 to 1.4=0, and for the right boundary pressure head was defined from zero to 0.5=0.5 and from 0.5 to 1.4= 0; the two other angles were zero flux.( attached plots for the left and right boundary as left and right boundary)
Expected results= that cross section for second project for pressure head from 0.8 to 0.5 should be the same as first project.(attached as cross section sample)

Comsol results=they are not like each other!!!!

Do you have any idea that what is the problem in comsol?
Thanks in advance for your valuable comments.
Sepideh
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