Solving - Latest Discussions - COMSOL Forums

No speedup when using distributed memory cluster

Wed, 23 May 2012 17:54:43 +0000

I wanted to see if someone could help me determine why I am not seeing any speedup when I submit jobs on multiple nodes of my HPC cluster (using the distributed memory capability).

I understand that speedup is highly model dependent. Per the suggestions of previous discussion threads, I have tried numerous different models with different physics (both linear and non-linear problems). Also, I have tried large memory models and small memory models (also per previous thread recommendations). Below are my results using the COMSOL Model Library Example "Micromixer Cluster Version":

Micromixer_cluster.mph (mesh as given):
1 node; 1 proc.: Run time = 123 sec
1 node; 12 proc.: Run time = 38 sec
4 nodes; 12 ppn: Run time = 99 sec
8 nodes; 12 ppn: Run time = 223 sec

I see speedup when I go from 1 proc. to 12 proc. running on 1 node (shared memory), but I don't see speedup, in fact I see slowdown, when I try to distribute the job across multiple nodes (distributed memory). The step-by-step instructions said to try refining the mesh for better speedup (this was also COMSOL support's recommendation). Here are the results for 2 different refined meshes:

Micromixer_cluster.mph (refined mesh):
1 node; 1 proc.: Run time = 566 sec
1 node; 12 proc.: Run time = 130 sec
4 nodes; 12 ppn: Run time = 259 sec
8 nodes; 12 ppn: Run time = 501 sec

Micromixer_cluster.mph (super-refined mesh):
1 node; 1 proc.: Run time = 1169 sec
1 node; 12 proc.: Run time = 414 sec
4 nodes; 12 ppn: Run time = 614 sec
8 nodes; 12 ppn: Run time = 896 sec

Still no speedup. Only slowdown.

Has anyone seen any speedup on this COMSOL Model Library example? If so, I'd be interested in your results.

One thing that I am doing that is different than the COMSOL recommendation is submitting jobs through the command line rather than through the Desktop. Does anyone know why COMSOL recommends submitting batch cluster jobs through the Desktop and not through the command line? Could this be my issue?

Any help would be appreciated.

Cotinuous Release in Particle Tracing Module

Tue, 22 May 2012 19:27:54 +0000

I would like to continuously release particles for a set amount of time using the new particle tracing module. Under hte Inlet settings there only seems to be the availability of step-wise release times. Is there any way to implement continuous release in this module? Or should I so a quasi-continuous release, ie: setting the interval time to a very small value?

Stationary and Time-dependent study for Joule Heating

Tue, 22 May 2012 02:14:35 +0000

Hello,

I am working on a rather simple simulation of Joule Heating on a Pt resistor deposited on AlN substrate. Although I can perform the stationary study and have some of the results I want, I cannot perform a time-dependent study. The execution fails with error message "Failed to find consistent initial values. Last time step is not converged.".

Any ideas what might be wrong?

Cheers!

-O.

failed to evaluate variable Jacobian

Mon, 21 May 2012 09:14:09 +0000

Hi,

I am trying to simulate particles using mathematical particle tracing model

of comsol 4.0. But I am getting the following error when I am trying to solve it:

Failed to evaluate operator Jacobian.
- Variable: px
- Geometry: 2
- Boundary: 1

I have attach the file. Please give me a help.

Thanks!

marx

How to get the derivative of a force with respect to a self defined variable?

Mon, 21 May 2012 06:47:46 +0000

Hi All,

I am working on a simulation of a particle moving in water.

The particle moving velocity is V and its value is 0.01m/s, which we can define as a moving boundary condition.

Then COMSOL can calculate the hydrodynamic force (F) on the particle by integrating the hydrodynamic tensor (for example,T_z_chns and T_r_chns in a 2D axisymmetric geometry).

But, question is how I get the derivative of F with respect to V?

I guess coupled variable in comsol should be used as well as matlab.

Any experts can help me out?

Stationary study failed to converge

Fri, 18 May 2012 18:06:45 +0000

Hello, I am trying to do a stationary of a MEMS device, but Comsol keeps failing to converge.

Some background on the model:
The model is a MEMS consisting of a plate attached to 4 thin cantilever beam springs, which are in turn attached to a fixed substrate. The plate is also attached to a set of combs whose teeth act as capacitors with a set of corresponding combs attached to the fixed substrate (see attached image. Everything not in purple is attached to the plate and should be free to move). A voltage is applied to the fixed combson one side of the device, while the plate itself is grounded. This causes the plate to be displaced until the capacitive force from the comb capacitors is balanced by the restorative force of the springs.

Comsol Physics setup:
I am using the Electromechanics physics node in Comsol 4.2a to do a stationary study on how much the plate is displaced. I placed all domains in Linear Elastic material model, fixed the boundaries shown in purple in the image, applied a voltage to the three fixed combs in the right of the image, and grounded the center plate. I then created a stationary study and computed. Unfortunately, the solver fails to converge. Is there something wrong with the way I have set everything up? Does anyone have suggestions about what may be going wrong?

Josh

Cluster job that shows speed-up when using multiple nodes

Thu, 17 May 2012 00:51:01 +0000

Hi,

I would be highly interested if someone could post an mph model file that they have shown to see speed-up when distributed across multiple nodes. I am having difficulty seeing any speed up for a number of models and understand from previous threads that speed-up is highly model dependent.

If someone could post an mph file that they know to show speed-up it would be greatly appreciated.

Best regards,
Josh Thomas

Convergence issues for transient freezing (apparent heat capacity phase change)

Tue, 15 May 2012 23:49:38 +0000

Hello,

I am fairly new to COMSOL and am trying to solve a transient (over 600 seconds) freezing (phase change) problem in a gel (similar thermal properties to water). I am using temperature-dependent thermal conductivity and density (both implemented as cubic-smoothed lookup functions, f(T) ). I am simulating the phase-change with the apparent heat capacity method (also implemented as a cubic-smoothed lookup function, f(T) ).

Across the model, my temperatures vary from 140K to 300K, with fairly high temperature gradients near the cooling interface (order of 40K/mm).

I have a 2D geometry with phase change occurring over <1K, that solves without issue. However, I have a slightly more complicated 3D geometry that I am having problems converging. I can get the solution to converge, treating the phase change as a triangular function over >30K, but the solver gets hung up for any more aggressive phase change.

I would like to reduce the temperature duration over which my phase change is implemented (less than 10K). I am assuming a triangular “pulse” will provide the most gradual change for specific heat, but is this an incorrect assumption and will another function provide less of an issue for convergence? Is there any other settings I can look at to help with convergence? I am using the default settings for the transient solver.

Any assistance you can offer would be greatly appreciated.

Thanks!
Michael

Simple convection model not converging

Tue, 15 May 2012 19:12:31 +0000

Hello all,

I have a simple beam model in which the beam is made out of silicon and it is sorrounded by air. When I apply a voltage to the beam, it creates temperature gradient along the beam due to the resistivity of the beam being dependent on the temperature at which it is at. To incorporate the convection due to the air, I went ahead and used two physics to mimic this phenomenon: electric currents (to compute the resistance of the beam and the power) and non-isothermal flow (to compute the temperature, including the effect of convection). The model itself is a one quarter model, allowing for symmetry, which I took care of with the simple boundary condition of electric and thermal insulation. The reason behind coupling these is so that I can see the effect of convection, given the fact that the heat transfer coefficient of air will change due to temperature. When I run my model with time dependent I get the following error:

"Failed to find consistent initial values.
Last time step is not converged."

When I run it with stationary I get the following error:

"Failed to find a solution.
Maximum number of segregated iterations reached.
Returned solution is not converged."

Any help is greatly appreciated.

Thanks.

Please give me some hints for a high Mach number turbulent modeling

Mon, 14 May 2012 22:59:28 +0000

Hello advanced users,

I am trying to model a fluid flow in a nozzle.
As there were too many error with the initial conditions, (e.g. Attempt to evaluate real square root of negative number...)
I referred some initial values from a tutorial 'Sajben diffuser'.
After input the values, that error was solved, but still there is a problem with

''Undefined value found.
Detail: Undefined value found in the equation residual vector.
There are 57 degrees of freedom giving NaN/Inf in the vector for the variable mod1.nutilde''

When I checked the log file, a variable 'mod1.nutilde' seems to be diverging, and it makes the error.
How can I fix this error?
Thanks a lot in advance.

Regards
MJ

initial solution problem

Sun, 13 May 2012 00:06:54 +0000

In a time dependent model I input a parameter as a function contains logarithmic part. put the program stopped at the initial step because there is a large difference between initial value and boundary value so the program give me fluctuated values beside the boundary ,where some values reaches to negatives .so the logarithmic part of the function gives error

COMSOL discretization

Fri, 11 May 2012 05:07:41 +0000

Hi,

I read in the reference manual that underlying discretization method of COMSOL is Galerkin method. Galerkin method is a weighted residual method and it does not require weak form. However, it looks like COMSOL converts the equations to weak form. So, what is the underlying discretization method in COMSOL?

I am not familiar with discontinuous Galerkin method. By any chance, is this the method used by COMSOL?

Thanks,
Sirisha

Solving model with several ModelNodes

Thu, 10 May 2012 16:19:23 +0000

Hi,
I'm trying to build a model that contains several ModelNodes (sub-models). Each Node should have different properties (same geometry but I want to alter the mesh). The the Model should be solved at once.

My questions are:
How to set dependent variables (since the sub-models should not be coupled)?
How to access the solution for each ModelNode?
Are there some examples available (couldn't find anything about this in the Comsol 4.2a documentation)?

Best regards,
CS

Air flow through elbow channel

Wed, 09 May 2012 14:38:40 +0000

Hi all!

I have problem with simulation of flow of air through the elbow channel. I have the box 500x50x80mm with the fi 50mm inlet from 50x80mm side and whole base (500x50) is an outlet with grill which should ensure flow only in normal direction (see attached model).

The task I am facing is to obtain the pressure distribution at the outlet.

I think my problem is connected with proper meshing of the problem and setting the boundary conditions, but still I cannot obtain any solution.

The usual errors I get are that the limit of Newtonian iterations have been reached.

Could you help me with making this model to run?

Best regards,
Michał Radziwon

linux cluster distribute computing no speed up

Wed, 09 May 2012 07:50:39 +0000

cluster configuration:1head node+8nodes，32cores each node，64GB ram each node。

comsol：comsol4.0 floating network licence installed on the head node, intel mpi

mpi file: COMSOL40\models\ACDC_Module\Verification_Models\parallel_wires.mph the air domain is increased in order to get more DOF, stationary study, direct solver MUMPS
test process:
Step 1. Solve this problem in 1 node using 16 cores
Step 2. Solve it in 4 nodes using 16 cores each node

test result: the solution time is almost the same (about 100 seconds), no speedup is obtained. It seems that all the nodes do the same thing.

Please check the folowing logs and help me out please, Thanks a lot.

PBS log for Step 1
------------------------------------------------------------------------------
--- Starting job at: Wed May 9 10:58:22 CST 2012

--- Current working directory is: /home/lubo/comsol
--- Running on 16 processes (cores) on the following nodes:
16 node5
--- mpd BOOT
/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verbose
running mpdallexit on node5
LAUNCHED mpd on node5 via
RUNNING: mpd on node5
--- mpd TRACE
--- Parallel COMSOL RUN
/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log
--- mpd ALLEXIT

--- Job finished at: Wed May 9 10:59:57 CST 2012
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Starting job at: Wed May 9 10:58:22 CST 2012
--- Current working directory is: /home/lubo/comsol--- Running on 16 processes (cores) on the following nodes: 16 node5--- mpd BOOT/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verboserunning mpdallexit on node5LAUNCHED mpd on node5 via RUNNING: mpd on node5--- mpd TRACE--- Parallel COMSOL RUN/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log--- mpd ALLEXIT
--- Job finished at: Wed May 9 10:59:57 CST 2012--------------------------------------------------------------------------------------------------------------------------------------------------------------- Starting job at: Wed May 9 10:58:22 CST 2012
--- Current working directory is: /home/lubo/comsol--- Running on 16 processes (cores) on the following nodes: 16 node5--- mpd BOOT/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 mpd boot -f /var/torque/aux//1723.mgmt -mpirsh ssh --verboserunning mpdallexit on node5LAUNCHED mpd on node5 via RUNNING: mpd on node5--- mpd TRACE--- Parallel COMSOL RUN/home/lubo/comsol/COMSOL40/bin//comsol -nn 1 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log--- mpd ALLEXIT
--- Job finished at: Wed May 9 10:59:57 CST 2012------------------------------------------------------------------------------

PBS log for step 2

------------------------------------------------------------------------------
--- Starting job at: Wed May 9 11:04:36 CST 2012

--- Current working directory is: /home/lubo/comsol
--- Running on 64 processes (cores) on the following nodes:
16 node5
16 node3
16 node2
16 node1
--- mpd BOOT
/home/lubo/comsol/COMSOL40/bin//comsol -nn 4 mpd boot -f /var/torque/aux//1724.mgmt -mpirsh ssh --verbose
running mpdallexit on node5
LAUNCHED mpd on node5 via
RUNNING: mpd on node5
LAUNCHED mpd on node3 via node5
LAUNCHED mpd on node2 via node5
LAUNCHED mpd on node1 via node5
RUNNING: mpd on node3
RUNNING: mpd on node2
RUNNING: mpd on node1
--- mpd TRACE
--- Parallel COMSOL RUN
/home/lubo/comsol/COMSOL40/bin//comsol -nn 4 -np 16 batch -inputfile test.mph -outputfile out_test.mph -batchlog test.log
--- mpd ALLEXIT

--- Job finished at: Wed May 9 11:06:31 CST 2012
------------------------------------------------------------------------------

license logs for step 2
.....
11:01:05 (lmgrd) LMCOMSOL using TCP-port 46447
11:03:00 (LMCOMSOL) TCP_NODELAY NOT enabled
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node5
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node2
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node3
11:03:00 (LMCOMSOL) OUT: "CLUSTERNODE" lubo@node1
11:03:08 (LMCOMSOL) OUT: "ACDC" lubo@node5
11:03:08 (LMCOMSOL) OUT: "COMSOL" lubo@node5
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node5
11:04:49 (LMCOMSOL) IN: "ACDC" lubo@node5
11:04:49 (LMCOMSOL) IN: "COMSOL" lubo@node5
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node1
11:04:49 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node3
11:04:50 (LMCOMSOL) IN: "CLUSTERNODE" lubo@node2

comsol bach output for step 1

*******************************************
********COMSOL progress output file********
*******************************************
Wed May 09 10:58:25 CST 2012
---------- Current Progress: 100 %
Memory: 348/348 1048/1048
Current Progress: 0 %
Memory: 370/370 1065/1065
---------- Current Progress: 100 %
Memory: 387/387 1082/1082
Current Progress: 0 %
Memory: 527/527 1359/1359
Linear solver
Number of degrees of freedom solved for: 1484195
- Current Progress: 10 %
Memory: 526/527 1379/1379
- Current Progress: 13 %
Memory: 932/932 1885/1885
- Current Progress: 15 %
Memory: 1125/1125 2057/2057
-- Current Progress: 27 %
Memory: 1068/1125 2003/2057
--- Current Progress: 30 %
Memory: 876/1125 1812/2057
Symmetric matrices found.
--- Current Progress: 31 %
Memory: 1230/1230 2958/2958
--- Current Progress: 32 %
Memory: 1254/1254 2958/2958
--- Current Progress: 33 %
Memory: 1279/1279 2958/2958
--- Current Progress: 34 %
Memory: 1298/1298 2958/2958
--- Current Progress: 36 %
Memory: 1318/1318 2958/2958
--- Current Progress: 37 %
Memory: 1359/1359 2958/2958
--- Current Progress: 38 %
Memory: 1383/1383 2958/2958
--- Current Progress: 39 %
Memory: 1399/1399 2958/2958
---- Current Progress: 40 %
Memory: 1421/1421 2958/2958
---- Current Progress: 41 %
Memory: 1448/1448 2958/2958
---- Current Progress: 42 %
Memory: 1460/1460 2958/2958
---- Current Progress: 43 %
Memory: 1481/1481 2958/2958
---- Current Progress: 46 %
Memory: 1497/1497 2958/2958
---- Current Progress: 48 %
Memory: 1514/1514 2958/2958
----- Current Progress: 50 %
Memory: 1533/1533 2958/2958
----- Current Progress: 52 %
Memory: 1549/1549 2958/2958
----- Current Progress: 54 %
Memory: 1562/1562 2958/2958
----- Current Progress: 56 %
Memory: 1580/1580 2958/2958
----- Current Progress: 59 %
Memory: 1597/1597 2958/2958
------ Current Progress: 60 %
Memory: 1622/1622 2958/2958
------ Current Progress: 62 %
Memory: 1628/1628 2958/2958
------ Current Progress: 64 %
Memory: 1647/1647 2958/2958
------ Current Progress: 67 %
Memory: 1662/1662 2958/2958
------ Current Progress: 68 %
Memory: 1682/1682 2958/2958
------- Current Progress: 70 %
Memory: 1693/1693 2958/2958
------- Current Progress: 73 %
Memory: 1710/1710 2958/2958
------- Current Progress: 75 %
Memory: 1726/1726 2958/2958
------- Current Progress: 77 %
Memory: 1753/1753 2958/2958
------- Current Progress: 78 %
Memory: 1762/1762 2958/2958
-------- Current Progress: 81 %
Memory: 1777/1777 2958/2958
-------- Current Progress: 83 %
Memory: 1796/1796 2958/2958
-------- Current Progress: 85 %
Memory: 1811/1811 2958/2958
-------- Current Progress: 87 %
Memory: 1828/1828 2958/2958
--------- Current Progress: 90 %
Memory: 1844/1844 2958/2958
Iter Damping Stepsize #Res #Jac #Sol
---------- Current Progress: 100 %
Memory: 2161/2161 3284/3284
1 1.0000000 0.53 1 1 1
Total time: 91.721 s.

comsol batch output for step 2

*******************************************
********COMSOL progress output file********
*******************************************
Wed May 09 11:04:41 CST 2012
---------- Current Progress: 100 %
Memory: 361/361 1061/1061
Current Progress: 0 %
Memory: 383/383 1082/1082
---------- Current Progress: 100 %
Memory: 395/395 1091/1091
Current Progress: 0 %
Memory: 543/543 1375/1375
Linear solver
Number of degrees of freedom solved for: 1484195
- Current Progress: 10 %
Memory: 657/657 1592/1592
- Current Progress: 13 %
Memory: 1269/1269 2365/2365
-- Current Progress: 20 %
Memory: 1122/1269 2057/2365
-- Current Progress: 27 %
Memory: 1079/1269 2016/2365
--- Current Progress: 30 %
Memory: 904/1269 1842/2365
Symmetric matrices found.
--- Current Progress: 31 %
Memory: 1141/1269 2391/2391
--- Current Progress: 33 %
Memory: 1158/1269 2391/2391
--- Current Progress: 35 %
Memory: 1178/1269 2391/2391
--- Current Progress: 37 %
Memory: 1195/1269 2391/2391
--- Current Progress: 39 %
Memory: 1216/1269 2391/2391
---- Current Progress: 41 %
Memory: 1227/1269 2391/2391
---- Current Progress: 43 %
Memory: 1244/1269 2391/2391
---- Current Progress: 45 %
Memory: 1261/1269 2391/2391
---- Current Progress: 47 %
Memory: 1283/1283 2391/2391
---- Current Progress: 49 %
Memory: 1305/1305 2391/2391
----- Current Progress: 52 %
Memory: 1321/1321 2391/2391
----- Current Progress: 54 %
Memory: 1338/1338 2391/2391
----- Current Progress: 55 %
Memory: 1363/1363 2391/2391
Iter Damping Stepsize #Res #Jac #Sol
--------- Current Progress: 94 %
Memory: 1318/1363 2545/2545
1 1.0000000 0.53 1 1 1
---------- Current Progress: 100 %
Memory: 1853/1853 3262/3262
Node 1:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Node 2:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Node 3:
Linear solver
Number of degrees of freedom solved for: 1484195
Symmetric matrices found.
Iter Damping Stepsize #Res #Jac #Sol
1 1.0000000 0.53 1 1 1
Total time: 108.638 s.

Infinitely long cylinder as a simple harmonic oscillator

Mon, 07 May 2012 02:51:53 +0000

This is a very simple problem. An infinitely long rigid cylinder with a given diameter and density functions as a simple harmonic oscillator with a given spring constant (per unit length). So this is a 2D problem. How to find the eigenfrequency with Comsol? Later I intend to couple this oscillator to a fluid etc.

Error: Failed to find time step so that given tolerances are satisfied

Fri, 04 May 2012 12:03:27 +0000

Error: Failed to find time step so that given tolerances are satisfied

This is the error that Generalized-alpha gives. I think the BDF solver in similar cases gives the error
"Cannot meet error tolerances. Increase absolute or relative tolerance."

This happens in odd situations. For example, I have a parameter that, if I set it to 0.1, the error doesn't happen, 0.15, it DOES happen, for 0.2, 0.3, 1.0, it doesn't happen. If I adjust the absolute tolerance, then for 1.0 it DOES happen, but for 1000 it doesn't happen. There seems to be no clear way to characterise when it occurs. All I know, is that it happens around the same time in the simulation as a boundary condition changes according a (smoothed) step function (in time). There is a generous amount of smoothing.

My question is: Why does it happen at all?

In my general understanding of solvers, there should always be a reasonable time step at which the error will be small enough. If there is too much error, then we reduce the time step. And this is what the solvers seem to be doing. But all of a sudden, there is a time in the simulation, when reducing the time step by 5 or 6 orders of magnitude, compared to what's normally needed, does not reduce the error enough.

I'm trying to build an understanding of this behaviour.

I've tried adjusting many of the solver parameters. So far, most of them don't have an effect on the issue, except Amplification for high frequency. (This is for Generalized alpha.) What is this, and why does it make a difference? I've checked the User and Reference documentation, and there is very little information, except to say that it's "damping of higher frequencies".

This issue is really causing a lot of trouble. Even at fairly modest amplitudes of the step in BCs.

Trouble coupling heat transfer physics for both fluids and solids

Wed, 25 Apr 2012 09:19:20 +0000

Hey all,

So I'm getting stuck with my model where I try to couple three different physics. The three physics are: Electric Currents, Heat transfer in Solids, and Heat transfer in Fluids. Basically what I'm trying to model is a silicon microbridge which is doped, which makes it so that it has a temperature gradient accross it when heated. I am able to couple and run the electric currents and heat transfer in solids physics, where the power dissipated from the ec physics is inputed into the ht physics as the heat source, and then the temperature that is calculated is used to calculate a new resistivity value for the silicon, until the model converges to a value for the temperature at the given voltage.

The problem arises when I try to incorporate the ht2 physics to mimic the effects of natural convection from the sorrounding gases. I set a temperature boundary condition within the ht2 physics which tells the program that the temperature of the microbridge is given by T, which is calculated in the ht physics. However, when I run this, I get the following error:

"Constraing found for variables in different Segregated groups. Try to merge these groups.
-Feature: Stationary Solver 1 (sol1/s1)
-Error: Constraint found for variables in different Segragated groups. Try to merge these groups."

Any ideas? Attached you will find my model. Thanks.

PML error

Sun, 11 Mar 2012 22:20:16 +0000

Hi all,

Can someone point me what I do wrong?
I tried to repeat Scattering from plasmonic nanosphere model, so I have Au sphere + Air domain (sphere) +PML/ABC domain (sphere).

When I defining PML as spherical type I'm getting error that Comsol could not find any spherical or cylindrical regions.

Determine Arrenhius damage integral for a solution

Thu, 13 Aug 2009 00:05:07 +0000

I am trying to apply an Arrenhius damage integral DURING the solution of an electrosurgical problem using the Bioheat Transfer Module along with the Conductive Media DC module (T and V are the dependent variables) . The integral is of the form:

Adi = int(A*exp(-E/(R*T),t)

where Adi is the Arrenhius damage integral, int stands for integral and A, E, and R are constants. T is the nodal tissue temperature and t is time.

Is there a way to apply this into the Global Equations by taking the derivative of Adi? Thus making the equation:

Adit = A*exp(-E/(R*T)

I tried this, but received an error that T could not be solved for. Do I need to do something in order for Global Equations to access my dependent variables?

Thanks for any help...I am also interested in any other way that anybody can think of!