Latest Discussions - COMSOL Forums

PDE solver with non-linear terms

Thu, 30 Jan 2025 14:31:06 +0000

Hi COMSOL Community,

I am trying to solve a PDE that I derived, which does not follow the conventional equation formats available in the existing modules. Therefore, I am using the PDE solver in COMSOL. To define my governing equation, I had to use two coefficient PDEs (u1 and u2) and link them together.

I am also utilizing the Generalized Alpha Implicit solver; however, my simulation fails after a few time steps when using an initial condition. I am unsure whether I have incorrectly defined my governing equations or if I am encountering some computational limits.

Could you provide guidance on this issue? I have attached my setup for reference.

Best regards, AA

To model an electromagnetic MEMS

Thu, 30 Jan 2025 05:04:54 +0000

Fellow forum members,

I am working on modeling an electromagnetic MEMS-based 1D scanning mirror (image attached) that operates using copper coils for actuation. My goal is to simulate the physics behind this system to determine:

Whether it can achieve the desired scan speed
The mirror’s displacement for a given current input.
The mirror's deformation for the scan speed.
Variations in the scanning path due to the structural shape of the MEMS.

As I am new to COMSOL, I would appreciate your insights on whether this is the right platform to achieve these objectives. If so, where should I start?

I have watched some informative videos in the Learning Center on thermal actuators, and I strongly believe that COMSOL has the necessary capabilities for this type of modeling. However, I am looking for a stepping stone—such as an example, a relevant article, or a structured guide, specifically electromagnetic mems —to help me get started.

Any help in this regard would be greatly appreciated. Thank you for your time!

Best regards,

Simulation of battery for convection through phase change material

Wed, 29 Jan 2025 20:16:52 +0000

I need help developing a 2D simulation of convection for a battery fully immersed in phase change material (PCM). Heat transfer occurs through the PCM to the surroundings via convection from all sides. The battery acts as a constant rectangular heat source.

Please guide me.

Fluidic Chamber Design

Wed, 29 Jan 2025 18:10:08 +0000

Hello,

I have an Inlet in the form of a cylinder of radius 0.5mm. I need to tapper it so that that it at the bottom becomes a rectangle of length 1mm and height 0.1mm. How can I build this geometry? Thanks

coupling coefficient of ring resonator

Wed, 29 Jan 2025 03:54:14 +0000

Hi all,

I am trying to calculate the coupling coefficient of ring resonator with a straight waveguide. I constructed the physical structure but still do not know how to apply the equation of coupling coefficient to get the value. i attached the equations.

Any help with that

Calculate radius of curvature v4.2a

Tue, 28 Jan 2025 14:55:08 +0000

Hello,

I was hoping someone could advise me on how I can calculate the curvature and radius of curvature of a 2D plane curve in v4.2a.

I believe that newer versions have this function built in but I unfortunately don't have access.

Thanks!

Seeing 3D mesh as 2D surfaces

Tue, 28 Jan 2025 13:46:45 +0000

I performed mesh in my 3D geometry and when I use clipping tool, I cannot see the 3D mesh part, I see only 2D surface meshes.

Thermo-mechanical analysis: unexpected results

Tue, 28 Jan 2025 10:36:54 +0000

Hi everyone,

I am studying the effect of the thickness of a copper plate at a constant temperature of 660 °C. I have performed the coupling between thermal and mechanical aspects, and I found that the displacement increases with an increase in thickness, which seems unusual. Could you please provide some guidance on where I might have made an error? Thank you for your assistance!!

Can COMSOL plot gaussian beam intensity distribution 2D and 3D? And how?

Sun, 26 Jan 2025 21:47:00 +0000

Hi I am Onur. I am trying to make Fabry-Perot interferometer system on Comsol using Ray optics module. I set up my beams to be Gaussian beams. Also, I added ray detectors to detect Intensity of the beams which is coming perpendicular to ray detectors. My question is can I make a plot that gives me the intensity distribution of Gaussian beams? And how do I do that?

Thanks.

Predicting %reflectance and %transmittance of 3 mm thick nanofiber layer from 0.05 mm thick nanofiber layer in COMSOL Multiphysics

Sat, 25 Jan 2025 14:07:12 +0000

I have determined %reflectance and %transmittance of 0.05 mm thick nanofiber layer in COMSOL. To reduce computational cost, I need to determine %reflectance and %transmittance of 3 mm thick nanofiber layer from 0.05 mm thick nanofiber layer. How to determine %reflectance and %transmittance of 3 mm thick nanofiber layer from 0.05 mm thick nanofiber layer in COMSOL Multiphysics using Radiative Transfer Equation?

Graphene oxide material

Sat, 25 Jan 2025 05:47:35 +0000

I am using COMSOL 5.3 for implementation of graphene oxide for better stability of sensor. Can anyone suggest values of properties of graphene oxide in COMSOL or any suggested reference material to refer?

Display only Deformed Geometry in Results Node

Fri, 24 Jan 2025 23:15:27 +0000

This is a pretty basic question, but I have searched online and haven't been able to find an answer. I am performing a Static/Stationary structural simulation, and when I create a Results-Volume-Deformation node, I see the deformed geometry overlaid with the undeformed wireframe. Is there a setting to turn off the display of the undeformed geometry in this node?

Changing dimension, geometry and meshing in joule heating module

Fri, 24 Jan 2025 18:04:54 +0000

Hi,

I have a model where I need to add a function of Temperature to change dimensions of sides of an octagonal shape. In my case, let's say side 1,3,5,7 will increase length and to maintain the shape side 2,4,6,8 will contract from both ends. The change of length dimension will be a function of temperature. Can someone please guide me how to do it? Thank you. I guess moving mesh is an option, but this is a unique case for me. Thank you.

Exporting results from the command line with no access to desktop app. Modifying Security preference 'File system access'.

Fri, 24 Jan 2025 16:21:30 +0000

I am trying to run a COMSOL method on my university's super computer, so I only have access to COMSOL via the command line. My method does the following:

model.study("std1").run();
model.result().export("data1").run();

And I am executing this on the command line with

comsol batch -inputfile iso_sym.mph -methodcall methodcall1

model.study("std1").run(); seems to be executing just fine. But I get the following error when running model.result().export("data1").run();:

AccessControlException: Security preference 'File system access' does not allow 'write' access to ...

So, I think I need to change Security preference 'File system access' to allow write to all files, but how do I do that from the command line?

Microfluidic channel simulation

Fri, 24 Jan 2025 02:22:44 +0000

I want to simulate my microfluidic channel model. Anyone who can assist me in detailed procedure? Anyone who can help in managing time dependent study and solvers?

Microkinetic Modeling in COMSOL

Thu, 23 Jan 2025 18:55:29 +0000

Oxidative coupling of methane (OCM) is interesting both industrially and fundamentally due to its coupled heterogeneous-homogeneous mechanism. Therefore, I would like to model it in COMSOL. However, the reactions involve many radical intermediates, such that kinetic mechanisms can quickly contain 50+ gas phase species and 10+ surface species with many hundred reactions. Up to what size can COMSOL handle kinetic mechanisms and are there any options I need to select, like switching to a solver that can handle stiff problems? Any advice is greatly appreciated.

Validating Biot Savart law

Thu, 23 Jan 2025 13:10:39 +0000

I am attempting to validate the magnetic flux density value from theoretical calculations to COMSOL modeling.

I have calculated the magnetic field intensity at a point located at the midpoint of a finite 1-meter wire carrying 1A current, positioned 1 meter away from the wire, which amounts to 8.9 × 10^-8 Tesla (T).

I am modeling this using COMSOL's 3D AC/DC interface and have created the geometry as described. The central cylindrical structure represents the current-carrying wire, and the surrounding cylindrical enclosure is an air boundary. I have specified a wire thickness of 0.05 meters and assigned copper as the material. The boundary structure is assigned air properties. I have created a point inside the air cylindrical surface exactly 1 meter away from the midpoint of the current-carrying wire. I am studying the magnetic flux density (B) in tesla (T). However, I am obtaining a value of 2 × 10^-7 T, which does not match my calculated value.

I would appreciate suggestions on what might be causing this discrepancy.

If possible, could you provide more details about your theoretical calculation method and the specific COMSOL settings you've used?

Regards,

Navaneeth

image:

Modeling Anisotropic Silicon

Wed, 22 Jan 2025 19:59:12 +0000

I want to learn how to model silicon substrates based on their orientation such as 100, 110, 111. My end goal is to model anisotropic silicon etching. I would appreciate any guidance as to achieve this.

Thanks

Heat Transfer, Condenser Heat Exchanger with fouling

Wed, 22 Jan 2025 18:48:00 +0000

Hello, I would like to ask about the heat transfer simulation on the condenser model with fouling (using Asphalt (tar) material) that I did, because the simulation data shows that the temperature of the hot fluid drops more quickly than the thickness of the fouling.

Problems in Lunar Drilling Mechanical Model

Tue, 21 Jan 2025 19:43:47 +0000

Hi,

I am implementing a mechanical model to characterize the interaction between a drill and lunar regolith. I am basing the model in a paper that has analytical and test results so I can validate it later. From the simulations I need to retrieve the reaction Force and Torque between the drill and the regolith, considering that the former rotates and penetrates with defined velocities.

Initially I wanted to have a time-dependent study, but after trying for a couple of months without getting any results, I decided to move to a stationary case to assess both the force and torque at different depths. After some time I could make it converge and give what seems to be good results.

However, COMSOL does not allow to include a prescribed velocity of the drill in the stationary case (which makes sense) but I need to find a way to include a condition that recreates this velocity. I have tried to include a prescribed deformation, but I am not getting the results I expected.

I would like to ask for some recommendation to include a condition that recreates this penetration speed in the stationary case or, if possible, some advice to make the time-dependent solver converge. I am attaching a Google Drive link to the model in case you need it.

Thank you so much in advance!

(Link: https://drive.google.com/file/d/1GaoCKnW7yVVwVJ1-vpFyl1yktSUpQzp9/view?usp=sharing )