Latest Discussions - COMSOL Forums

How to Export Mode Shapes (Vertical Displacement) in COMSOL 5.2

Sat, 13 Sep 2025 02:44:48 +0000

Hi everyone,

I’m currently modeling a plate because I want to obtain its mode shapes and corresponding natural frequencies. I’ve been able to get those results, but now I’d like to export the mode shapes (specifically the vertical displacement ? as a function of ? and ?) and I’m not sure how to do it.

In the Results tab, I see Surface 1, and under that, I have Deformation, but I can’t find a way to export the data. I’m using version 5.2.

Any guidance would be greatly appreciated.

Thanks in advance

Why does 2D static deformation plot show displacement magnitude smaller than the Y-axis displacement?

Fri, 12 Sep 2025 17:09:34 +0000

In this model, the color-scale (displacement magnitude, ~0.1mm) deformation does not match the XY spatial deformation of the plot (~20mm). Can someone help me understand how the displacement magnitude is different from what is plotted in XY space?

Force and torque change with conditions

Fri, 12 Sep 2025 13:51:44 +0000

One type of simulation (multibody dynamics) I want to achieve is to apply a certain external force and torque on an object, with the requirement that the magnitude of the applied external force and torque changes continuously with displacement. It should be such that the magnitude of the force and torque is just enough to cause displacement. How should I set this up?

Material Properties Reference

Fri, 12 Sep 2025 13:24:37 +0000

Hello,

I am working COMSOL Multiphysics 6.3 for quiet a while now and would say I have quiet a bit of experience.

However I have one big issue. I can not get the references for material properties from the COMSOL library. I tried multiple approaches to get that information:

1) As described in the Material Library User guide: In Materials -> Browse Materials -> Select Material and Property. The property reference window just displays no text at all for any material or property I select.

2) Checking in File -> help -> documentation -> Comsol Multiphysics -> Reference Manual -> Materials -> Module-Specific Material Libraries: The source listed here for the piezoelectric materials is the efunda website, which in itself has some books listed but not property specific and non of the books seems to have matching properties to the one COMSOL uses. Some values may be the same but never the set of values I list below. That applies for the CRC Handbook, the MEMS handbook and the Macmillan properties.

3) Checking the online reference manual -> materials -> module specific material databases. There are no sources named for piezoelectric materials and the ones for MEMS are the same as on the efunda webpage but as I said they do not match the values in COMSOL. For example youngs modulus for gold is 70e9 in COMSOL but in the books listed 78e9.

I want references for Youngs Modulus, Poisson ratio and density for: Au, Pd, SiO2 I want references for Coupling matrix, elasticity matric, relative permittivity and density for: Lithium Niobate and Gallium Arsenide

How do I obtain proper sources? Is there a bug in the first option I list? That seems to be the way one is supposed to get that information.

Thanks for any help.

Lumped port problem (Element 1 should be placed between two conductive boundaries)

Thu, 11 Sep 2025 13:53:51 +0000

When I placed the lumped port in the CPW design the error showed - "Subfeature Uniform Element 1 should be placed between two conductive boundaries. - Feature: Uniform Element 1 (ue1) " - I placed the lamped port in between the perfect electric conductor boundary, still this error message came and stopped the process. Can anyone check the file attached and give me the advise to correct this? I already go through the examples COMSOL provide, but can not understand the problem. Also the ground and ports are not connected to each other (separated by a air gap).

1D-Plot the Deformation of a Line / Edge

Thu, 11 Sep 2025 12:18:02 +0000

Hi again,

I wanna plot the deformation (shape) of an outer edge / line of a 3D-structure before and after applying an external load. The undeformed shape I obtain via a 1D-plot using the expression z over x or the arc-length out of an edge 3d node under results. The displacement I obtain via a 3D-cut line. But how can I obtain the position z over the length x in the deformed state? I´m only able to get the undeformed state. But the information about these coordinates must be available in the results, since the 3D-Plot shows the deformation. Maybe one can use the mesh nodes along that line/edge? Pls give me a hint, I´m dealing with that topic for 4 days now.

Thanks,

BR Sven

Comsol Multiphysics 4.2a for Windows

Tue, 09 Sep 2025 17:47:38 +0000

Good afternoon everyone. I hope you are all well.

I have a permanent license for Comsol Multiphysics version 4.2a, but I can't find the installation CD for this version.

This version isn't available on the Comsol website. Can anyone help me? Thank you in advance. Best regards;

Automated Mesh-Based Reassignment of surface Boundaries in COMSOL

Mon, 08 Sep 2025 16:36:02 +0000

Hi all,

I’m working on a AC/DC COMSOL model where I need to move the terminal and ground boundaries to different spots along a specific surface in my geometry. Right now, I pre-define several possible boundaries and manually assign the conditions for each run, but this gets unwieldy for automated or parametric studies.

I’m looking for a more automated (or programmatic) way to do this, ideally using outputs from each simulation to update the positions of these boundaries for the next iteration.

Specifically, I’m interested in any method that allows me to reassign boundaries based on the mesh. The boundaries themselves don’t have to “move” geometrically, as long as I can programmatically select new mesh nodes or elements as the new terminal or ground (using the initial surfaces as a reference and translating the assignment from there), that would be perfect.

Has anyone done something similar, or does anyone know of features, best practices, or scripting approaches (using MATLAB/LiveLink, Java API, etc.) that could help? My current model uses manual pre-tagged surfaces, but I’d love to streamline this process.

I have attached my current model where the surfaces are pre-defined and assigned manually. Right now, I pre-define several possible circular surfaces and manually assign the terminal and ground to the top two circular surfaces. For each new simulation, I want these boundaries to shift to the next two circles, and continue in this way. I would greatly appreciate any guidance or resources to help automate this process.

Thanks in advance for any ideas or suggestions!

1D-Plot from 3D Symmetry Data

Mon, 08 Sep 2025 14:45:53 +0000

Hi,

I got a simple model of a roller under load. Due to the symmetry along the length of the roller, just the half is simulated via a symmetry node and visualized via a 3d mirror node and a 3d edge in the results data set. That works as it should for the 3d evaluation. But if i wanna evaluate (plot) the displacement (shape) of the outer body edge of the roller, I just can pick the one half of the original split half geometry model. So now the question: Is it possible to "copy" or "mirror" also the symmetric displacement (shape) data to show the whole geometry's displacement (shape) at the 1d-Plot? Btw, a 3d line doesn´t work, since the outer shape of the roller is not straight but curved.

Thanks for any recommendations,

BR Sven

Measuring Interface position as a function of Time in COMSOL (Two-Phase Flow, Level Set)

Mon, 08 Sep 2025 11:31:55 +0000

Hello everyone,

I am modeling a wicking phenomenon in COMSOL Multiphysics using the Two-Phase Flow, Level Set method with Laminar Flow. My main challenge is extracting the wicking height (or interface position) as a function of time.

I have attempted to use the Cut Line method to track the fluid-fluid interface (phils = 0.5), but so far I have not been able to properly obtain the wicking height vs. time.

If anyone has experience with this or knows a reliable way to correlate the interface position with time in COMSOL, I would greatly appreciate your guidance.

Thank you in advance for your help!

Convergence issue using Richard's equation

Tue, 02 Sep 2025 16:48:09 +0000

Hi everyone,

I am working on a hydraulic model. The geometry of my model is shown in the attached Figure. I am using Richard's equation. There are host rock that occupies most of the model, a fault shown as the narrow pipe, and other formations at the top right.

The general water flow process is that the inflow is through the top boundary with topography and outflow is through right boundary and top boundary when water table intercepts the surface, which means that pressure head at the top is higher than zero.

For boundary conditions, a constant precipitation was applied at the top boundary with topography, which is in green in the figure. A pressure head of 0 Pa was applied at the top of fault. For the rest top part, a previous layer was applied and it will be applied a big conductance when pressure head is higher than zero. Otherwise, a conductance of 0 will be applied.

The main object of these settings was to ensure that the location of the water table can be dynamic determined by the precipitation rate and permeability instead of applying a constant head at the top.

However, when I use Time-dependent solver for cases that don't have a steady state, the solver does not converge/converges slowly. The solving progress usually stays at 4% and does not move on. If anyone has any insights about how to make it converge or improve my model, i would really appreciate it! Please let me know if more information is needed. Thank you!

Best, Zihao

Implementing Direction-Dependent Etching Velocity in COMSOL Deformed Geometry

Sat, 30 Aug 2025 16:29:07 +0000

Hi everyone,

I am trying to reproduce the chemical etching tutorial from COMSOL (link: https://www.comsol.com/model/chemical-etching-44481 ). In the tutorial, they used Prescribed Normal Mesh Velocity in Deformed Geometry to describe the etching velocity, where the velocity value is constant. In my case, I would like to define a non-uniform etching velocity, meaning that the velocity in the x-direction is different from the velocity in the y-direction. I tried some approaches, but they didn’t work. Could you please give me some suggestions on how to implement this?

Thank you so much!

Color legend

Sat, 30 Aug 2025 03:36:53 +0000

I wanted to change the height and position of the color legend, but I couldn't find it

Undefined Value in Temperature Field (NaN/Inf in comp1.T)

Fri, 29 Aug 2025 10:01:39 +0000

I am currently working on a numerical simulation of a plasma torch using COMSOL Multiphysics. The goal of the simulation is to model the behavior of a plasma jet generated by an electric arc discharge between an anode and a cathode. As part of the setup, argon gas is injected through the torch, which becomes ionized due to the high-temperature environment created by the electric discharge. This ionized gas forms a plasma jet that exits the torch and interacts with an open boundary, representing ambient surroundings or downstream flow.

The simulation includes the following coupled physics:

Electric currents to model the arc discharge.

Laminar or turbulent fluid flow for argon gas transport.

Heat transfer to capture thermal effects and plasma temperature distribution.

Open boundary conditions to allow outflow of plasma without artificial reflections.

However, when I run the model using the Stationary Solver, I encounter the following error message:

Feature: Stationary Solver 1 (sol1/s1) Undefined value found. Detail: Undefined value found in the equation residual vector. There are 2590 degrees of freedom giving NaN/Inf in the vector for the variable comp1.T. At coordinates: (0.0176092, 0.298922), (0.0143478, 0.3), (0.0163046, 0.298921), ...

Extracting data in 3d format

Thu, 28 Aug 2025 15:59:56 +0000

So far, I have been extracting abs(emwHz) values for given parameter in a 2D cutplane in my loop antenna model. I would like to extract it in a 3D grid format.

However, most methods of trying a grid 3D dataset has resulted in errors, where Hz is an undefined variable, like as shown below.

"Undefined variable. - Variable: comp1.emw.Hz - Global scope Failed to evaluate expression. - Expression: comp1.emw.Hz"

Is there a way to overcome this error, or if not, to obtain Hz values in a 3d format?

LiveLink for Creo is very slow

Thu, 28 Aug 2025 09:24:57 +0000

It seems that the time required to import a model from PTC Creo to COMSOL increases exponentially with the number of components.

At some amount of surfaces, or solids, or boundaries, or whatever - I have not managed to figure out what exactly triggers the slowdown - the time required seems to go to infinity.

Looking at the status bar a ticker walks leisurely like "generating associativity for entity 7734 of 12995" and sometimes it just stops at "processing selections" and waits for half an hour. Or fails entirely after prolonged waiting. Which is odd since I have no selections defined in Creo.

Importing the same model as a STEP is massively faster, but then I lose associativity with all the rest of the features, boundary loads, shell thicknesses, et cetera - and have to rebuild it every time.

Can this be improved? I have no high hopes, since I suspect it is a consequence of the Java interface to Creo - which is why I post it here as a concern and suggestion rather than a support issue.

High aspect ratio

Thu, 28 Aug 2025 08:58:07 +0000

I have a fracture that is represented in terms of a layer in porous media of domain size 15001500500m and the fracture is situated in center. I'm not able to create proper mesh. Also, the mesh that i have created, the solution is not converging for it.

Particle tracing module

Wed, 27 Aug 2025 08:08:14 +0000

Can particle position be referenced as an independent variable in the electrostatic module?

Simulating Electrocapillary effect

Tue, 26 Aug 2025 15:24:28 +0000

I am trying to simulate droplet motion under Electrocapillary Force. I have two electrolytes, one as the droplet and the other as the continuous phase. I tried to couple the TDS and ES physics to form the EDL, but the droplet motion does not occur. Do I need to define surface tension based on the Lippmann equation as well, or is creating the EDL alone sufficient to change the surface tension?I am using a 2D geometry and applying a DC voltage. I have set velocity inlet and pressure outlet as boundary conditions, but at the inlet the velocity is 0.

I define space charge density in each species as : F_Const( C_cation-C_anion).

Trial Passcode

Tue, 26 Aug 2025 14:33:18 +0000

Hi guys,

I am trying to download a trial version but its asking the Passcode which I don't have, can any one please help me with this.