Latest Discussions - COMSOL Forums

Cluster sweep for a time-dependent study

Sun, 09 Aug 2020 11:38:53 +0000

Hi,

I have a time-dependent study that I'm trying to make parametric sensitivity analysis for it using a remote high-performance cluster.

To speed up the process and distribute the job to many nodes, I'm using cluster sweep instead of a parametric sweep. Additionally, I detached the study to solve for a certain parameter, and attached another study to solve separately for another parameter, in order to save time.

The problem is: I get results with skipped steps (meaning, the time dependent-study is skipping time intervals while solving). I understand that this can happen if the solver configuration and time stepping are set to be free instead of strict. However, I already set the default solver for the time-dependent study to be strict. Am I missing a step here? is there something else I should do?

Regards, Eman

3D-shell

Sat, 08 Aug 2020 06:39:01 +0000

Recently, I want to use comsol shell module to simulate the deformation of Kirchhoff thin plate and Mindlin plate. How should I set up the software to distinguish these two types of research?

Rising air bubble in turbulent water environment (multiphase)

Fri, 07 Aug 2020 23:01:05 +0000

I'm consistently running into the "No convergence, even when using the minimum damping factor" error. I want to model a multiphase system with an air bubble rising in turbulent water. The system is closed, so there are now flows, just the water moving due to being heated. I'm using a time-dependent study w/ phase initialization (a stationary soln cannot be found). No matter how much I refine my mesh, I cannot get it to converge. I've implemented nonlinear computations and the works, and still no convergence. Can someone please give me some guidance? Here is the download link: https://secure.comsol.com/download/support/file/1/5/2/2/6/0/6/2/rising%20air%20bubble_turbulent.mph?gda=1596841166_41f23847b7931a3b58487404df89ce8b&fileExt=.mph

Circular coil

Fri, 07 Aug 2020 21:47:43 +0000

The below post is related to an archived discussion

[sHitart here] Hi! I'm trying to model a circular coil with a toroidal geometry. I want to see the magnetic flux density but I don't know how can I add the "gap feed". I have COMSOL 5.3a Thank you!

Saving accumulated probe table at time steps taken by solver?

Fri, 07 Aug 2020 12:36:24 +0000

I am doing a parametric sweep on my studies and am interested in the results recorded by a few probes. When running without the sweep, I select to update probe results at the times taken by the solver; however that probe table gets overwritten at every iteration of the sweep. Accumulated table instead only saves the probe results at times stored at output. To get higher resolution, I have to increase the number of time steps of the output, which hugely increases my model size as it saves everything at that resolution.

Is there a way of outputing the accumulated probe table at times taken by the solver instead?

Friday, August 14th Abstract Submission Deadline for COMSOL Conference 2020 North America

Fri, 07 Aug 2020 12:30:14 +0000

Hello COMSOL Community!

The final abstract submission deadline for the COMSOL Conference 2020 North America is coming up on Friday, August 14.

By presenting at the COMSOL Conference, you can:

Get recognition for your research and development work
Showcase your modeling and simulation expertise
Connect with colleagues across industries and academia
Gain valuable feedback from industry experts to help further your work

Accepted abstracts may be considered for Best Paper or Best Poster awards. All presenters and coauthors will receive a reduced registration rate.

For suggested topics, deadlines, and to submit an abstract, visit: www.comsol.com/conference/call-for-papers/north-america.

Dates & Locations:

COMSOL Conference 2020 North America - October 7-8: www.comsol.com/conference/north-america

COMSOL Conference 2020 Europe - October 14-15: www.comsol.com/conference/europe

How to use a cylindrical coordinate in solution？

Fri, 07 Aug 2020 09:25:10 +0000

I want to extract the rotaion angle of the model from the results, but I don’t know how to use the cylindrical coordinate system in post-processing. Help me please. In addition, I want to know why the deformations u, v, w in Comsol contain plural information. What does this mean?

Modeling Anisotropically Expanding Domain

Thu, 06 Aug 2020 23:00:13 +0000

Hi,

I am attempting to model a 2D reaction-diffusion system in which the overall domain size increases as a function of local concentration. I've done this using a deforming mesh and prescribed mesh velocity. However, I also need the mesh to expand from inwards in the case of a concentration peak inside the domain but zero concentration at the boundary, e.g., cell division. Is there a straightforward way of achieving this?

Thank you!

Instant decrease of the temperature after the voltage pulse

Thu, 06 Aug 2020 21:14:42 +0000

Hello, dear colleagues!

I am pretty new to COMSOL and nowadays I am making a model with the Heat Transfer in Solids module. I am applying voltage pulses to my structure and looking at the change of the temperature, that happens due to joule heating. The temperature distribution looks great if I apply nanosecond pulses. But as I start working with millisecond voltage pulses the temperature after the end of the pulse instantly decreases, the model has no gradual relaxation of the temperature at this time scale (even if the pulse heated the structure very much). Same thing happens with heating, the heating happens almost instantly. I have already tried to change all of the parameters, but it didn't work. What am I missing?

Thank you in advance and I wish you luck with your models!

Bulk temperature

Thu, 06 Aug 2020 17:41:13 +0000

Hello I am simulating annular flow in 3D. I want to write the expression to calculate bulk temperature in 3D but every time I faild. Can COMSOL experts can help me to write this expression

Meshing 2D Material

Thu, 06 Aug 2020 02:57:59 +0000

Hello!

I am new at using COMSOL Multiphysics, and I am currently learning how to use it in order to simulate the heat flux across a 2D Material that is deposited between a heater bar and a sensor bar. I am currently struggling to mesh the model because the aspect ratio of the thin film is so high (I made my thin film as a block of dimensions 0.2um, 10um, and 6A). I was wondering if there was a way to possibly maybe make seperate meshes for the rest of the model and the deposited material, or if there was another work around for this issue.

Thank you, Annalies Tipton

Optical microscope image simulation

Wed, 05 Aug 2020 22:40:22 +0000

i am trying to simulate an optical microscope image of a 4 micron diameter sized particle which is placed between an analyzer and a polarizer under 400-700 nm white light.

Particle has internal ordering of small platelets which gives rise to maltese cross pattern much like liquid crystals. I have tried using the RF module to simulate the scattered field in plane polarized light. Do you think Enorm^2 would be what i am seeing as my optical microscope image? or the far field is being projected on the camera in optical microsocpe? any help or guidance will be greatly appreciated.

Dynamically create export data file name

Wed, 05 Aug 2020 18:03:37 +0000

Hello, I want to export data after simulation. I would like to include the variables I defined in the Component 1 > Definitions > Variables section into my output file name. For example, if I use T = 300K, bias voltage = 1V, dopant concentration (N_D) = 10 um^-3, I want the output file name to be something like that T_300K_V_bias_1V_ND_10um^-3. I don't want to input the filename manually because it is cumbersome. Is there a way to export the file automatically?

Simulation of 2D and 3D optical fiber for frequency domain for mode analysis and boundary mode analysis using comsol 5.5.

Wed, 05 Aug 2020 11:43:48 +0000

I want to know how to simulate 2D & 3D optical fiber. (Actually I simulated 2D already). I am facing problems in 3D. Just guide me regarding boundary conditions ie condition for scattering at entry and exit. Should I apply scattering condition at core or cladding or at both.? Conditions at Port. whether single port is enough or need to apply port at both ends. Should I apply port at core or cladding or both.? What is role of polarisation in boundary mode analysis.? How to apply it.? You can suggest some model or references and simulated desigh as well. Also sometimes it gets out of memory during meshing and computation. any critical information regarding meshing. Tell me something about limitation of system. I am using 32 gb RAM. Anything relating to domains of geometry limiting the outcome. Thanks in advance.

Electrical currents in porous media

Wed, 05 Aug 2020 03:54:58 +0000

Hello!

I am doing simulation of saturated by water sand rock (porosity 0.35). No flow of water, but on the side borders I am applying eleсtric potential difference. Electrical current pathing through water accumulate temperature raising in the rock.

However I can not combine two modules: Electrical current and Heat transfer in Porous media. Comsol requires heat transfer parameters for rock and water, but electrical parameters - only for rock, without water. It can not do both.

How to solve this problem? Am I using wrong modules?

Thank you!

geometry updating from matlab through comsol livelink

Wed, 05 Aug 2020 03:47:19 +0000

how do i update the values in comsol for matlab and matlab for comsol?

question about small imaginary part for eigenfrequency

Tue, 04 Aug 2020 23:08:28 +0000

Hello all,

I am running a study for acoustic in a hard wall cylindrical tank. The problem can be easily solved by separation of variables. Theoretically, the eigenfrequencies are all real. But why the eigenfrequencies solved in comsol included imaginary part, such as 1847.9832949527051+8.535829728636379E-12i. All imaginary parts are very small which are compared with real parts. How and why does this imaginary part exist? I am really confused about this part.

Regards.

Margaret

Draw point graph for difference between two points

Tue, 04 Aug 2020 17:03:00 +0000

I have 2D time dependent simulation of cooling. I have created two "Cut Point 2D" in the Results/Data Sets. I can draw line graph for boths points using "1D Plot Group" and two "Point Graph" inside. The result graph is the change of temperature with time in boths points.

But I need to draw the difference of temperature in these two points as function of time. Any hints?

Calculation of dielectrophoretic force on a line

Tue, 04 Aug 2020 07:08:47 +0000

Hi,

I am performing a 2-d simulation in COMSOL 5.5 in which a microfluidc device separates different cells using dielectrophoresis. I want to compute the dielectrophoretic force acting on different particles on a vertical line. I have tried the built-in expressions from COMSOL, but they do not work out (maybe I do not know how to do such an action). Does anyone know how could I do that?

Issue regarding coupling piezoelectric and Fluid surface interaction

Mon, 03 Aug 2020 15:27:50 +0000

Hello,

I am trying to simulate piezo actuated valve. I am having some problems with couplaing piezo and fluid surface interaction. I have used moving mesh for fluid domain however, the fluid domain does not seem to move according to the structural deformation (caused by piezo). I have used fully coupled along with iterative solver. However, I seem to get this error.

Feature: Stationary Solver 1 (sol6/s1) Undefined value found.
- Detail: Undefined value found in the equation residual vector. There are 218 degrees of freedom giving NaN/Inf in the vector for the variable comp1.spatial.u. at coordinates: (-0.00045691,-0.0002), (-0.000503455,-0.0002), (-0.000410365,-0.0002), (-0.000496554,-0.000191171), (-0.000451259,-0.000190817), ...

There are 218 degrees of freedom giving NaN/Inf in the vector for the variable comp1.spatial.v. at coordinates: (-0.00045691,-0.0002), (-0.000503455,-0.0002), (-0.000410365,-0.0002), (-0.000496554,-0.000191171), (-0.000451259,-0.000190817), ...

Can someone please let me know what could be the problem?