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Need to change circular planner shape to hexagonal
https://www.comsol.com/forum/thread/350591/need-to-change-circular-planner-shape-to-hexagonal?last=2025-04-03T08:17:27Z
<p>Hi,</p>
<p>I wish to change the circular coil to hexagonal in 3D.
Take a look the 3D design,</p>
<p>Suggest me what to do in Geometry>workplane>plan geometry>rectangular .</p>
Thu, 03 Apr 2025 08:17:27 +00004.2025-04-03 08:17:27.350591Absorption Coefficient
https://www.comsol.com/forum/thread/350582/absorption-coefficient?last=2025-04-03T00:44:01Z
<p>I want the syntax to compute the absorption coefficient and I want to know if it could be calculated from the absorption cross-sectional area</p>
Thu, 03 Apr 2025 00:44:01 +00004.2025-04-03 00:44:01.350582Hollow Fiber Membrane Modeling
https://www.comsol.com/forum/thread/350572/hollow-fiber-membrane-modeling?last=2025-04-02T20:51:12Z
<p>Hi,</p>
<p>I am new to COMSOL and I am attempting to recreate the hollow fiber membrane modeling that was performed in this presentation.</p>
<p>https://www.comsol.com/video/modeling-co2-removal-with-hollow-fiber-modules-in-comsol-aug-20-2018</p>
<p>I was able to recreate most of it but when I click compute I get the following error.</p>
<ul>
<li>Feature: Stationary Solver 1 (sol1/s1)
Failed to evaluate initial residual for segregated step 1.
Undefined variable.
<ul>
<li>Variable: comp1.nirf1.rho</li>
<li>Geometry: geom1</li>
<li>Domain: 3
Failed to evaluate variable.</li>
<li>Variable: comp1.spf.rho</li>
<li>Defined as: comp1.nirf1.rho
Failed to evaluate expression.</li>
<li>Expression: dvol_spatial<em>(r</em>(pi<em>((-((d(comp1.u,r)</em>comp1.u)+(d(comp1.u,z)<em>comp1.w)))</em>(2*comp1.spf.rho))))
Failed to evaluate Jacobian of expression.</li>
<li>Expression: (2<em>comp1.spf.rho</em>(-(d(comp1.u,r)<em>comp1.u+d(comp1.u,z)</em>comp1.w)<em>test(comp1.u)-(d(comp1.w,r)</em>comp1.u+d(comp1.w,z)<em>comp1.w)</em>test(comp1.w))<em>pi</em>r)*(dvol_spatial)</li>
</ul></li>
</ul>
<p>I attached the mph file any help would be greatly appreciated.</p>
<p>Thanks,</p>
<p>Juan</p>
Wed, 02 Apr 2025 20:51:12 +00004.2025-04-02 20:51:12.350572solvers when there are coupled modules or not
https://www.comsol.com/forum/thread/350563/solvers-when-there-are-coupled-modules-or-not?last=2025-04-02T05:52:42Z
<p>For the same dimension (1d, 2d...), is the solver always the same for all modules?</p>
<p>Does the software always automatically adjust the solver when there are more than one module (even when the modules being solved don't share the same unknows, aren't related or coupled at all)?</p>
Wed, 02 Apr 2025 05:52:42 +00004.2025-04-02 05:52:42.350563How to induce voltage from PZT-5A to copper coil, which is kept at a distance of 40 mm ?
https://www.comsol.com/forum/thread/350561/how-to-induce-voltage-from-pzt-5a-to-copper-coil-which-is-kept-at-a-distance-of-40-mm?last=2025-04-02T05:29:14Z
<p>Hey there,</p>
<p>I'm a newbie in comsol and trying to solve one problem.
A piezoelectric material, PZT-5A is being applied by an impact force of 1000 N, now due to stress there's some accumulation of charge in PZT, and I've also applied magnetic field in the surrounding, Now I want to check an induced voltage on a copper coil which is kept at <strong>40 mm or less</strong> distance by PZT.</p>
<p>I'm trying everything, yet there has been no success, can anyone please help ?</p>
<p>P.S. The geometry is 2d axis symmetric.</p>
Wed, 02 Apr 2025 05:27:00 +00004.2025-04-02 05:27:00.350561About RF MEMS switches in reconfigurable antennas.
https://www.comsol.com/forum/thread/350551/about-rf-mems-switches-in-reconfigurable-antennas?last=2025-04-02T05:19:05Z
<p>Hi all,
I am currently doing one project in RF MEMS switches which i can use for Frequency selective surfaces or reconfigurable antennas. The issue is that how we can incorporate this RF MEMS switch in Frequency selective surfaces or reconfigurable antennas in order to observe the mechanical, electrical and electromagnetic properties. I am confused that how all the modules will work together to get the results</p>
<p>Thank you</p>
Wed, 02 Apr 2025 05:19:05 +00004.2025-04-02 05:19:05.350551Inverted mesh element - phase change interface deforming geometry
https://www.comsol.com/forum/thread/350541/inverted-mesh-element-phase-change-interface-deforming-geometry?last=2025-04-01T18:47:22Z
<p>Hi,</p>
<p>I have been getting this error and this warning:</p>
<p>The following feature has encountered a problem:
- Feature: Automatic Remeshing 1 (sol1/t1/ar1)
Failed to find consistent initial values.
Last time step is not converged.</p>
<p>Inverted mesh element near material frame coordinates (0.0499996, 87998.2).
In Material Frame Variables:
There was an error message from the linear solver.
The relative error (1) is greater than the relative tolerance.</p>
<p>I am trying to create a moving boundary problem so my geometry is deforming, I am assuming this is what may be causing inverted mesh elements.</p>
<p>I have tried adding an automatic re-meshing node and refining my mesh around the deforming boundary.</p>
<p>I am new to COMSOL so any help would be appreciated, thanks.</p>
Tue, 01 Apr 2025 18:47:22 +00004.2025-04-01 18:47:22.350541Transient magnetic field: mimic a wire
https://www.comsol.com/forum/thread/350532/transient-magnetic-field-mimic-a-wire?last=2025-04-02T00:12:19Z
<p>Hello, I have built a solid mechanics and magnetic fields multiphysics simulation. At a high level, the simulation includes a current-carrying wire (that generates a magnetic field), and a small, soft-magnet device at some distance from the wire. In the presence of the magnetic field, I study the deformation of the soft magnetic structure.</p>
<p>I now want to do this simulation in a transient domain, however I would like to eliminate the need to simulate the field from the wire. Instead, I would like to specify or easily generate a field with the same exact profile as the wire. The reason for this is that COMSOL is giving me trouble when I attempt to study the coupled physics involving the current carrying wire while in a transient domain. If I can instead specify a transient magnetic field (not coming from a wire, just a "magic" field, if you'd like), then I can avoid this problem.</p>
<p>I have made this field already by using the MFNC module and specifying the Hx Hy and Hz. It runs fine. However, I am wondering if there is/are better ways to do this?</p>
<p>Thank you.</p>
Tue, 01 Apr 2025 18:46:45 +00004.2025-04-01 18:46:45.350532prism based SPR sensors simulation
https://www.comsol.com/forum/thread/350531/prism-based-spr-sensors-simulation?last=2025-04-01T19:17:37Z
<p>Hello, I am doing the SPR sensor design on COMSOL, i have done my structure(Upside down the prism, and other layers onto the prism), assigned the materials, and properties also. Now I have to give the ports and Scattering Boundary Conditions. Can you help?</p>
Tue, 01 Apr 2025 09:02:20 +00004.2025-04-01 09:02:20.350531Problem With ODE Time Dependent Study
https://www.comsol.com/forum/thread/350502/problem-with-ode-time-dependent-study?last=2025-03-31T21:08:03Z
<p>I have in my simulation some variables. They are converging correctly but when I add a ODE that is not coupled with those other variables, my solver doesn't converge anymore. All variables is not converging. Someone could explain to me what is happening? I'm using segregated solver, so, in theory this variable doesn't affect the other because they are uncoupled.</p>
Mon, 31 Mar 2025 21:03:02 +00004.2025-03-31 21:03:02.350502Running Batch Sweep with Batch commands
https://www.comsol.com/forum/thread/350501/running-batch-sweep-with-batch-commands?last=2025-03-31T14:04:21Z
<p>Hi All,</p>
<p>Is there a way to run a Batch Sweep using batch commands? I'm trying to execute a huge parametric sweep with Batch Sweep to speed up the overall simulation. I'd like to initiate the simulation with a batch command, but it seems to only perform a parametric simulation. (The simulation took the same amount of time as a normal parameter sweep, and the individual sub-simulations do not appear in the batch folder.)</p>
Mon, 31 Mar 2025 13:50:01 +00004.2025-03-31 13:50:01.350501Persistent error with undefined variable in time dependent solver and stationary solver
https://www.comsol.com/forum/thread/350491/persistent-error-with-undefined-variable-in-time-dependent-solver-and-stationary-solver?last=2025-03-31T13:55:25Z
<p>Hello Comsol,</p>
<p>I am facing an issue in my COMSOL model that I have been unable to resolve for a few days now, even after multiple attempts and fixes. I am working on a time-dependent simulation of blood flow in the aorta (normal aorta and with coarctation), and I have added Global ODEs (RCR model) to model the pressure changes in the arteries. My Boundary conditions have been set to velocity inlet and outlets with pressure. My main issue is that when I try to run the simulation, I keep encountering the error:
"Undefined variable - Variable: comp1.p"
This happens both in time-dependent and stationary solvers. How do I fix this issue?</p>
<p>(C_B*comp1.pt + comp1.p/R2_B - Q_B) this is the equation I have used in the global equation in global ODEs and DAEs. where:
C_B is the compliance
comp1.pt is dp/dt
R2_B is distal resistance
Q_B is the flow rate.
I have defined all these parameters.</p>
Mon, 31 Mar 2025 12:16:06 +00004.2025-03-31 12:16:06.350491Electrical and Thermal Characteristics
https://www.comsol.com/forum/thread/350483/electrical-and-thermal-characteristics?last=2025-03-31T09:32:08Z
<p>Hello everyone! I'm looking for a big guy in Beijing who is proficient in electric heat simulation, and I can pay a consulting fee if I have a question!</p>
Mon, 31 Mar 2025 09:32:08 +00004.2025-03-31 09:32:08.350483keep all plot features in matlab livelink
https://www.comsol.com/forum/thread/350473/keep-all-plot-features-in-matlab-livelink?last=2025-04-02T07:41:25Z
<p>There's a matlab file (function out = model) that creates a model, solves and postprocesses. All plot features including titles, legends are written within this model m function.
Then use mphplot(model,'pg') to plot 'pg'. But this loses all plot features. How to use mphplot while keeping all plot features without rewriting all features?</p>
Mon, 31 Mar 2025 05:08:55 +00004.2025-03-31 05:08:55.350473solvers: solving the same model with various equally suitable modules
https://www.comsol.com/forum/thread/350463/solvers-solving-the-same-model-with-various-equally-suitable-modules?last=2025-03-31T03:56:21Z
<p>The software automatically specifies solvers according to the specific modules used. When solving the same model with various equally suitable modules in one batch within the same mph file, by default only one solver is used for all the modules applied. This solver may be suitable for only one of the modules but not for the rest of the modules. In this case how to make the software use different solvers when solving different modules?</p>
Mon, 31 Mar 2025 03:55:06 +00004.2025-03-31 03:55:06.350463Issue in modeling natural convection to a pot
https://www.comsol.com/forum/thread/350462/issue-in-modeling-natural-convection-to-a-pot?last=2025-03-31T01:54:16Z
<p>I am trying to model the heat transfer to a pot in natural convection mode. This is an axisymmetric model, where a stove setup is modeled. The temperature at a bottom boundary (represents the burner) is set to a constant value. There is a pot placed on the stove. There is water (modeled as a solid object with a high thermal conductivity) inside the pot. We are studying the heat transfer to the pot and to the water through conduction and natural convection in this case.</p>
<p>I am using the heat transfer in solids and fluids, turbulent flow, and nonisothermal flow multiphysics coupling with a fully coupled solver to get the solution. The issue is that the bottom surface of the pot is getting heated, however, there is negligible temperature gain at the interior surfaces of the pot and also the water in the pot. What could be be possible issue? I am attaching the model .mph file for your reference.</p>
<p>Thanks!</p>
Mon, 31 Mar 2025 01:54:16 +00004.2025-03-31 01:54:16.350462Electrical and Thermal Characteristics
https://www.comsol.com/forum/thread/350453/electrical-and-thermal-characteristics?last=2025-03-31T00:39:40Z
<p>Hello everyone! Using a porous medium model to simulate Joule heat, it is known that the bed resistance decreases with increasing temperature, and the resistance and temperature data are obtained experimentally, fitted by an equation and then defined inside the material conductivity of comsol, why is the bed temperature change small?</p>
Mon, 31 Mar 2025 00:39:40 +00004.2025-03-31 00:39:40.350453Question about COMSOL tutorial provided
https://www.comsol.com/forum/thread/350452/question-about-comsol-tutorial-provided?last=2025-03-29T20:03:14Z
<p>Hello
I am trying to understand this tutorial
https://www.comsol.com/model/dc-corona-discharge-in-air-in-a-point-to-plane-configuration-100451
I want to change the wall boundary condition to just absorb the electrons and i want to plot it on the wall.
I am not able to do so. can you please tell me why.
My objective is to determine how much charge got deposited on the wall during the simulation</p>
Sat, 29 Mar 2025 20:03:14 +00004.2025-03-29 20:03:14.350452different time stepping under same 1D plot group
https://www.comsol.com/forum/thread/350443/different-time-stepping-under-same-1d-plot-group?last=2025-03-29T04:45:18Z
<p>I want to compute the same thing with 2 different time stepping and plot them under the same 1D plot group. The 2 different time stepping are plotted in line graph 1 (sol1) and line graph 2 (sol2) under 1D plot group.</p>
<p>Do I have to use different studies for different time stepping (yielding sol1 and sol2)? Different steps under the same study don't seem to allow different time stepping.</p>
<p>Is there any way of sweeping time steps in the parent node of 1D plot group? sol1 and sol2 are from different studies.</p>
Sat, 29 Mar 2025 04:45:18 +00004.2025-03-29 04:45:18.3504432D Simulation of PDMS Membrane with PEG-PCL-DA Hydrogel Reservoir
https://www.comsol.com/forum/thread/350432/2d-simulation-of-pdms-membrane-with-peg-pcl-da-hydrogel-reservoir?last=2025-03-28T19:38:23Z
<p>Hi,</p>
<p>I am trying to model the stress experienced within a PEG-PCL-DA hydrogel reservoir which will house cells. I am using a 2D, solid mechanics, time-dependent study to do so. I have created a rectangular membrane made of polydimethylsiloxane (PDMS) with a stationary end and a moving end, this end will be stretched at the strain rates 5%, 10%, and 12.5%. Within the rectangular membrane is a rectangular reservoir with the assigned material, PEG-PCL-DA hydrogel. The model is time dependent and is stretched for 0.2 seconds. I want to set up a cyclic time dependent study to include a retraction phase for 0.4 seconds after reaching a distance of 2mm, but am unsure about how to set up a piecewise or interpolation function. Any thoughts or advice? I have attached my .mph file for reference.</p>
Fri, 28 Mar 2025 19:12:13 +00004.2025-03-28 19:12:13.350432