Latest Discussions - COMSOL Forums

Unable to Start COMSOL, Facing Error

Sat, 21 Dec 2024 01:18:19 +0000

Getting the following error message when attempting to open COMSOL Multiphysics 6.2:

Could not obtain license for COMSOL Multiphysics GUI. License error: -15. Cannot connect to license server system. ** The license server manager (lmgrd) has not been started yet, the wrong port@host or license file is being used, or the port or hostname in the license file has been changed.** Feature: COMSOLGUI License path: C:\Program Files\COMSOL\COMSOL62\Multiphysics\license\license.dat;6601@a2.cmc.ca;6091@a2.cmc.ca; FlexNet Licensing error:-15,29

I tried addressing the items that were bolded but this same error remains. I believe the error is because of the 6091@a2.cmc.ca port that is mentioned in the license path. If this is the source of the error, how do I remove this from the license path?

Thanks for the help!

Ring in 2D in a side projection for Langevin

Fri, 20 Dec 2024 13:30:29 +0000

Good day. Please tell me how to draw a ring in 2D in a side projection so that the program perceives it as a whole element? Because when drawing it from the side, the ring looks like a rectangle torn in the middle. This is necessary for constructing a Langevin piezoelectric emitter in 2D. Even if these two pieces are combined in geometry, then when choosing a material, it still breaks it into two pieces.

Cannot evaluate variable

Fri, 20 Dec 2024 12:57:40 +0000

Hello everyone,

My question is about mach zehnder interferometer tutorial. You can find tutorial document in attachements.

After successfully creating structure, I finally reached point where I add electrostatic simulation for modulation. The error I got at this point is simulator cannot evaluate modulation voltage defined as V0.

The error I got is somewhat similar to the error given in the discussion below: The below post is related to an archived discussion

My error is

Undefined variable. - Variable: comp1.ewbe.epsilonrzz - Geometry: geom1 - Domain: 0 Failed to evaluate Jacobian of expression. - Expression: comp1.ewbe.epsilonrzz Failed to evaluate Jacobian of operator. - Operator: mean - Geometry: geom1 - Boundary: 3 Failed to evaluate Jacobian of variable. - Variable: comp1.ewbe.epsilonrzz - Geometry: geom1 - Boundary: 3 Failed to evaluate Jacobian of expression. - Expression: dvol_spatial((-mu0_const)((comp1.ewbe.iomegacomp1.ewbe.Jz_1)+(((-comp1.ewbe.dHdtx_1)(comp1.ewbe.alphaport_1comp1.ewbe.ny))-(comp1.ewbe.dHdty_1(-(comp1.ewbe.alphaport_1comp1.ewbe.nx)))))) Failed to evaluate Jacobian of expression. - Expression: (-mu0_const(-comp1.ewbe.dHdtx_1(test(comp1.ewbe.tEbm1zTy)+comp1.ewbe.alphaport_1test(comp1.ewbe.tEbm1z)comp1.ewbe.ny)-comp1.ewbe.dHdty_1(-test(comp1.ewbe.tEbm1zTx)-comp1.ewbe.alphaport_1test(comp1.ewbe.tEbm1z)comp1.ewbe.nx)+comp1.ewbe.iomegacomp1.ewbe.Jz_1test(comp1.ewbe.tEbm1z)))*(dvol_spatial)

Could you please help?

[start here]

How to only solve for stresses and strain and disable other quantities in Solid Mechanics Module

Fri, 20 Dec 2024 09:49:56 +0000

Hello! I hope everyone is doing well. I am trying to run simulations but the problem is that the simulation takes a lot of time and its taking a lot of space on the hard drive. So I want to solve only for stresses and strains and not other quantities in the solid mechanics modules like Guass stresses and Guass strains and strain energy and others. I would be glad if someone help me in this regard.

Objective function

Fri, 20 Dec 2024 09:34:30 +0000

How can I write objective function to enhance heat rate for cube and cylinder using following formula ? ( Topology optimization for Heat transfer) Q= 2 * Pi * K * L* (T1-T2) / log (r2/r1) for cylinder Q= KA(dt)^2 for cube [comp1.intop-------

To obtain the heat flux of the resonator in its operating mode, which research method should be used?

Fri, 20 Dec 2024 08:42:01 +0000

I have a resonator model, and the frequency of its operating mode is known. Which type of analysis should be used to calculate the heat flux at its operating frequency?

Boundary condition

Thu, 19 Dec 2024 18:59:15 +0000

Hello everyone,

I am working on a 1D model in the Heat Transfer in Solids (ht) module. I would like to improve a Robin boundary condition where I know the equation for the interface temperature, which varies over time, as follows:

Where:

T_SS(t): The temperature of my mold, which varies over time.
b_s and b_p The thermal effusivities of the steel (mold material) and the polymer (fluid), respectively.
T: The temperature from the previous step.

I tried to implement it only as a boundary temperature as

" if(t<=0, T_0, (T_SS(t)b_s + Tb_p)/(b_s + b_p)) "

but it doesn't work (T_0 is the initial temperature of my polymer ) I would appreciate any suggestions or guidance on implementing this. Thank you!

How to connect surfaces of unit cell in the whole model after deformation.

Thu, 19 Dec 2024 08:42:10 +0000

Hello everyone, Have a nice day

I have tried to read and mimic the simulation of sma_stent in application libraries in COMSOL. However, I can not understand how from an individual bar (unit cell) becoming a whole stent and why after deformation, these individual bars still connect each other?

I tried to my model but it does not work.

Could you please explain to me the reason?

I have attached the images about my simulation and sma_stent simulation in library of COMSOL.

Thank you for your time and consideration

java.lang.ArrayIndexOutOfBoundsException

Thu, 19 Dec 2024 08:20:19 +0000

Hello, when I open a NYhead_mesh downloaded from the Internet in COMSOL, COMSOL reports an error in the log file. java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 1 at com.comsol.util.classes.CsBitSet.a(SourceFile:84) at com.comsol.guigraphics.selection.SelectionModel.a(SourceFile:353) at com.comsol.guigraphics.AbstractGuiUpdateManager.a(SourceFile:998) at com.comsol.guigraphics.AbstractGuiUpdateManager.a(SourceFile:947) at com.comsol.guigraphics.AbstractGuiUpdateManager.a(SourceFile:559) at com.comsol.guigraphics.AbstractGuiUpdateManager.handleGuiEvent(SourceFile:237) at com.comsol.guigraphics.events.GuiEventManager.a(SourceFile:409) at com.comsol.guigraphics.events.GuiEventManager.sendQueuedEvents(SourceFile:440) at com.comsol.guigraphics.c.a(SourceFile:103) at com.comsol.bridge.ModelFeatureViewManagerAdapter.setGuiProperties(SourceFile:48) at com.comsol.guimph.l.a(SourceFile:572) at com.comsol.guimph.l.showNewView(SourceFile:305) at com.comsol.guimph.l.showNewView(SourceFile:274) at com.comsol.guimph.b.h.b(SourceFile:123) at com.comsol.guimph.b.h.a(SourceFile:59) at com.comsol.guimph.views.ModelBuilderViewInfo$1.modelContextChanged(SourceFile:51) at com.comsol.widgets.CsModelTreeContext.a(SourceFile:145) at com.comsol.widgets.CsModelTreeContext.treeSelectionChanged(SourceFile:132) at com.comsol.bridge.BridgeModelContext.treeSelectionChanged(SourceFile:47) at com.comsol.widgets.CsModelTree.a(SourceFile:239) at com.comsol.bridge.c.a.a(SourceFile:206) at com.comsol.bridge.c.a.d(SourceFile:195) at com.comsol.widgets.CsModelTree.e(SourceFile:468) at com.comsol.widgets.CsModelTreeContext.setContext(SourceFile:70) at com.comsol.guimph.x.c(SourceFile:427) at com.comsol.guimph.MphApplication.startApplication(SourceFile:67) at com.comsol.guimph.util.FileUtil.b(SourceFile:1234) at com.comsol.guimph.util.FileUtil.a(SourceFile:1202) at com.comsol.guimph.util.FileUtil$8.run(SourceFile:960) at com.comsol.guimph.progress.i$1.a(SourceFile:61) at com.comsol.guimph.util.u.a(SourceFile:25) at com.comsol.guimph.MphDesktopWindow.a(SourceFile:1724) at com.comsol.bridge.BridgeDesktopWindow.run(SourceFile:1142) at com.comsol.guimph.progress.i.a(SourceFile:71) at com.comsol.guimph.util.FileUtil.a(SourceFile:974) at com.comsol.guimph.util.FileUtil.open(SourceFile:937) at com.comsol.guimph.model.m.a(SourceFile:46) at com.comsol.guimph.util.FileUtil.a(SourceFile:1347) at com.comsol.guimph.util.FileUtil.openFile(SourceFile:1285) at com.comsol.bridge.command.ca$1.a(SourceFile:99) at com.comsol.guimph.util.l.apply(SourceFile:89) at com.comsol.guimph.util.FileUtil.checkPasswordAndApply(SourceFile:1408) at com.comsol.bridge.command.ca.a(SourceFile:102) at com.comsol.bridge.command.ca.b(SourceFile:75) at com.comsol.bridge.command.cn.c(SourceFile:35) at com.comsol.model.util.ReconnectThreadLatch.runWithoutWaiting(SourceFile:103) at com.comsol.bridge.command.cn.run(SourceFile:33) at com.comsol.bridge.command.l.c(SourceFile:213) at com.comsol.bridge.command.l.a(SourceFile:203) at com.comsol.bridge.command.l$1.run(SourceFile:94) at com.comsol.util.thread.SuspendableTasks$1.run(SourceFile:111) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source)

How to Input Power and Calculate COP in a Pipe Heat Transfer Simulation Using COMSOL?

Thu, 19 Dec 2024 04:48:59 +0000

Hello everyone!

I’m a beginner with COMSOL, and I’m currently working on a pipe heat transfer simulation. However, I’m having trouble setting up the power input and would really appreciate some guidance.

Goal: I want to simulate the heat transfer process in a pipe by inputting heating power, calculate the inlet and outlet temperatures of the fluid, and eventually use the results to determine the COP (Coefficient of Performance).

Cannot get the Electric Field lines and the contour doesn't show much difference.

Wed, 18 Dec 2024 17:47:54 +0000

Hi there,

I am new in COMSOL and trying to get longer field lines and electric field to show the difference of varying voltage and gap in an experiment. I am not sure what went wrong. If anyone can help me with this. I am attaching the file.

Regards, Nafeez

Questions about Mesh Sizing and Optimization for Accurate Displacement Measurement

Wed, 18 Dec 2024 11:03:10 +0000

Hello everyone, I hope you're doing well. I have a few questions regarding meshing and its impact on accurate displacement measurement. I am working on a structure designed to displace by 20 nanometers, and I facing some challenges in determining the optimal meshing parameters. I hope you're doing well. I have a few questions regarding meshing and its impact on accurate displacement measurement. I am working on a structure designed to displace by 20 nanometers, and I am facing some challenges in determining the optimal meshing parameters. 1. What would be the recommended minimum and maximum element size for the mesh to accurately capture this 20-nanometer displacement? 2. Considering that my structure is quite complex (including springs and several fingers for sensing), what meshing strategy or type would you recommend to ensure the most accurate results with minimal error? 3. Finally, does reducing the mesh size always improve accuracy? Or is there an optimal range for the mesh size beyond which further refinement does not provide significant benefits? As a side note: I have also attached the dimensions and size of the sensor finger and its gap (d1 and d2). In the attached figure, there is a 20-nanometer displacement along the x-axis in the d1 direction. I would greatly appreciate any advice, tips, or insights on this matter.

Outflow BC in coefficient form PDE

Wed, 18 Dec 2024 09:50:29 +0000

Several physics modules have an "Outflow" BC. The coefficient form PDE has not. Which is the best BC here to act as outflow BC? Can e.g. the "constraint" or "flux/source" BC be manipulated such that they act as one?

Data export

Wed, 18 Dec 2024 06:48:48 +0000

Hello, everyone!

I have a simple question, I want to use MATLAB for subsequent data processing, need to export all the data in a solution domain, how should I export?

Question about COMSOL notation

Tue, 17 Dec 2024 10:27:20 +0000

My question might sound pretty dumb but i can't find any information relative to the notation δ used as an operator in the documentation of COMSOL on this page at (3-212) https://doc.comsol.com/6.3/doc/com.comsol.help.sme/sme_ug_theory.06.087.html#4015992 Mathematically how is it defined ? Thanks in advance

Air cooling system for an array of PCB's using an air-tunnel

Tue, 17 Dec 2024 09:49:50 +0000

I only started working with COMSOL a month ago and had never simulated anything like this before. I set up a model where I have an array of 24 PCBs that I want to cool. Previously, I created a water-cooling system using a simplified form of heat pipes.

To simplify the simulation, I reduced the setup to 4 PCBs. These PCBs are 6-layer PCBs (i.e., 6 layers of copper with epoxy (FR4) in between). There are 4 heat sources on each PCB, with power ratings of 3×1.2 W + 1×0.66 W.

For the physics, I am using:

Heat Transfer in Solids and Fluids Laminar Flow

To simulate air cooling, I created an air tunnel surrounding the entire setup. In the Heat Transfer module, I defined an inflow with 20°C and an outflow. In the Laminar Flow module, I set up an inlet (average velocity = 20 m/s) and an outlet (pressure = 1 atm).

However, I keep encountering an error. For a test, I created a simulation with just a sphere surrounded by the air tunnel (much simpler than a series of thin layers), but I still get an error.

I now suspect that I might be doing something wrong when inserting a solid object into a gas (air). Can anyone help me with this issue? (Do you have experience with this?)

Creating a Permanent Magnet (Material-N52) in COMSOL 6.0

Tue, 17 Dec 2024 07:25:40 +0000

Hi!

I am new to COMSOL and trying to simulate the force experienced between two strips of N52 magnets of dimension "1.8mm x 1.8mm x 0.4mm". Six such magnets are kept stacked to each other such that two such strips face each other as shown in attached picture 1.

Since the magnet feature is not available in COMSOL 6.0, I used the "Magnetic Flux Conservation" under the "Magnetic Fields, No Current (mfnc)" study to carry out my simulation.
I obtained the data related to B-H curve of N52 and its coercive magnetic field from an open source software named "FEMM 4.2" which is also shown in attached picture 2.
The way I have input this material data about N52 from FEMM into COMSOL is shown in screenshot picture 3. Note that "Magnetic Flux Conservation 2" has been defined for upper block of magnets and "Magnetic Flux Conservation 3" has been defined for the lower block.
I intend to obtain the attractive force between the strips now. The screenshot 4 gives the result. The gap between the strips being 1.25mm. The force that is obtained is 0.32633 N. When I perform the same simulation in FEMM, the force turns out to be 0.219628 N (Screenshot 5). Question 1: I don't understand this discrepancy in the softwares, both being FEM and used extensively in industry. Is there something wrong in the way I am giving inputs to COMSOL?

Question 2: When I want to keep the magnets in a strip in a way that each adjacent magnet has oppositely aligned magnetization direction (i.e, if say a magnet has its magnetization vector (pointing from South to North) pointing in +z direction, then its adjacent magnets' magnetization vector must point in the -z direction). When I do this to both the strips, surprisingly the results turn out to be very different again and there's mismatch between both the softwares. Interestingly, COMSOL doesn't even show magnetic lines of force for the magnets which are magnetized in opposite magnetization sense, as shown in screenshot 6 (which also shows mismatch in forces again).

Can someone please help me as to what exactly is going wrong in my approach? Whether firstly, I am translating the information about N52 magnets correctly and secondly why is there a mis-match?

Thanking you in anticipation of your kind and earliest response in this regard.

Regards, Chetan.

Topology optimization of Transient heat conduction problem

Tue, 17 Dec 2024 02:53:10 +0000

Hi all! We are dealing with a transient topology optimization problem aiming at minimizing the amplitude of the temperature oscillation, as the following equation shows: where is the final number of the time step, is the spatial average temperature over the boundary at each time step, is the temporal mean of . For the time being, we set 2 global equations with expressions"d(T_ave,t)-T_sp " and "d(Psi,t)-T_sp-withsol('sol2', T_ave,setind(t,'last'))/t_range)^2)", with one time dependent step calculating for the physical field, global equation 1 and another time dependent step for global equation 2 and topology optimization respectively. It works for solving the objective function of the first optimization loop, but since the time dependent solver of the Optimization solver can only call time dependent step 2, the objective value keeps the same and won't be updated. We wonder whether there is method can fix this problem and implement the aforesaid objective function correctly.

Difference in capacitance results: COMSOL vs MATLAB

Mon, 16 Dec 2024 13:59:44 +0000

Hello everyone, I hope you're all doing well. I'm facing a significant challenge and would greatly appreciate it if you could help me out.

The capacitance I obtain for my structure using COMSOL is 38 femtofarads, but when I calculate the same structure in MATLAB, the capacitance increases to 54 femtofarads. I know that COMSOL takes fringing fields into account when calculating capacitance.

If anyone has experience with this or can help me identify where the issue might be, I would be truly grateful.

Thank you very much in advance!

Oscillations for a moving magnet in a coil

Sun, 15 Dec 2024 04:10:18 +0000

Hi,

I'm trying to model an electromagnetic energy harvester using as model the example COMSOL provides for induced voltage in a coil due to a moving magnet (https://www.comsol.com/model/voltage-induced-in-a-coil-by-a-moving-magnet-14163). Here the movement of the magnet is made through a moving mesh and a sinusoidal function.

I want to expand the model where the magnet oscillates due to an applied force and the oscillation are damped due to magnetic and mechanical damping of the spring of which the magnet hangs.

I think this can be made modeling the whole as a spring mass system. However I don't know much about the solid mechanics physics and i can't find an example that shows how to a model a simple spring mass system in 2D in COMSOL.

I would be very thankful for any advice and or direction that could help me carry out what I'm trying to model.

Best Regards