Latest Discussions - COMSOL Forums

Premixed Combustion

Wed, 15 May 2024 03:42:48 +0000

Hi,

So Im trying to build the methanol laminar premixed combustion in COMSOL. I used several physics interface like heat transfer in fluids, chemistry, transport concentrated species, and laminar flow. I used a single formula reaction rate (Arhenius reaction)

r = kexp(-E/RT)C_CH3OH^1.4

Eventhough, the temperature increase a lot, however the flame does not appear. Is anyone here can solve my prblem? or anyone knows about the setting in laminar premixed combustion in COMSOL?

I would really need help on this problem. I attached my file here

Rizky Kusumastuti

Scaling down issue in COMSOL Multiphysics from millimeter to micro meter

Tue, 14 May 2024 16:00:38 +0000

Hi Experts,

I have a model created and defined dimensions as parameters in millimeter range and I want to scale it down to micrometer dimension. I used the scaling option under geometry and add 1000 as scaling factor with isotropic option selected but after I clicked the build option, it processed the image and didnt show anything in the right hand side and sometimes it throws error saying "the object to be scaled must be selected".

I did select the CAD image as can be seen in the below screenshots image 2,image 3.

Am i doing some mistake in the whole scaling down process? could you please advise .I use COMSOL 2024 version. Is there any other way to scale down the parameters in comsol from millimeter to micrometer?

Image 2.png below is the inital image to be scaled but Image 3.png is the scaled image that vanishes when i click build all.

Kind reg Amit

A question about fluid-structure interaction

Tue, 14 May 2024 12:55:09 +0000

Why is the minimum temperature change in my FMI heat transfer simulation 5K, I want a more accurate temperature change, how should I do this, how should I implement the effect of microfluidic velocity on the FSI module

How to utilize Temperature Data for Complex Rolled Foil Geometry

Tue, 14 May 2024 12:53:24 +0000

Hello everyone,

I conducted a flow simulation (2D-axisymmetric) to obtain temperature data within a specific system. Now, I would like to utilize this temperature data for a separate study where the geometry is significantly more complex (a coated, rolled-up foil with over 3000 layers and layer thicknesses ranging from 5-60 µm).

Is there a way to directly transfer the temperature data from my flow simulation into a new study with the modified geometry? I am not particularly experienced with COMSOL. How would you suggest proceeding? Especially the thin and numerous layers are posing challenges for me.

Thank you!

Luis

Temperature difference boundary condition

Mon, 13 May 2024 12:47:26 +0000

Hello everyone,

I want to define a boundary condition in which there is a constant value for the temperature difference of two surfaces. How can I define such boundary condition?

Livelink for MATLAB taking too much time to simulate

Mon, 13 May 2024 11:46:57 +0000

Dear all,

    I am simulating coil strands to know its AC resistance. i am using LiveLink for MATLAB to automate this task. however, for 10 turns coil with 100 strands, the total simulation time goes to 5 hours while for 10 turns with 300 strands, the total simulation time goes 50+ hours.
    by profiler code checking, i found that *** model.sol('sol').runAll;*** is taking 95% of overall simulation time. can you please suggests me to reduce the time duration of simulations.
I am using regular mesh with minimal complexity. 

best regards
thanks

Problem with magnetic field, magnetostriction

Mon, 13 May 2024 11:40:05 +0000

Hi,

So Im trying to solve the core noise by magnetstriction in a three phase transformer. But Im having problems with the magnetic field. Directly when i try to solve it an An unexpected error occurred and its very hard to understand how to fix that anyone had same or any solutions?.

Tried to build the magnetic field same as this https://www.comsol.com/model/nonlinear-magnetostrictive-transducer-6063 But same thing An unexpected error occurred. And when i open log file its impossible to understand anything.

I would really need help on this problem.

Coil Geometry Analysis
Time dependent

Failed to Evaluate Variable Jacobian Error

Mon, 13 May 2024 00:57:41 +0000

Hello everyone!

I encounted this problem when I was trying to do a study(simulation) with Plasma module and Magnetic Fields Module in comsol. When I tried to include plasma domains to magnetic fields module, following error has happened. I attached my .mph file too!

The error message is following:

Feature: Time-Dependent Solver 1 (sol1/t1) Undefined variable.
- Variable: comp1.mf.iomega
- Geometry: geom1
- Domains: 10-11, 13, 29, 32, 53 Failed to evaluate Jacobian of expression.
- Expression: dvol_spatial(comp1.mf.dcomp1.mf.Jz) Failed to evaluate Jacobian of expression.
- Expression: (comp1.mf.d(-comp1.mf.Hxcomp1.mf.testcurlAx-comp1.mf.Hycomp1.mf.testcurlAy-comp1.mf.Hzcomp1.mf.testcurlAz+comp1.mf.Jxvar(comp1.mf.Adepx,comp1.A)+comp1.mf.Jyvar(comp1.mf.Adepy,comp1.A)+comp1.mf.Jzvar(comp1.mf.Adepz,comp1.A)))(dvol_spatial)

My FRF study is not showing anything

Sun, 12 May 2024 16:38:43 +0000

Hello! Please help me, when i do a study for frequency domain, in my results- nothing is showign? it is saying pressure, discplacement etc. is all zero, i dont understand why? I have chosen the entire geometry when performing the study. And when i perform an eigenfrequency study for the same construction, i get results but not when i perform an frequency domain study.

Transport of dilluted species and electrostatics

Sun, 12 May 2024 11:40:39 +0000

am studying the in fluence of suspended metallic dust particles in mineral oil under positive lightning impulse voltage . A cylidrical 1 litre point - plane test cell with a gap distance of 60 mm will be filled with mineral oil ( with and without contamination). The objective of the research is to determine the influence of suspended metallic dust particles on streamer velocity. A model has to be developed and simulation results have to be compared with experimental set results. How do l implement it using electrostatics and the transport of diluted species physics.

Your help is appreciated. I have been struggling for the past 6 month.

Regards

Amos

Counting Particle Types at Outlet for Particle Tracing for Fluid Flow feature

Sat, 11 May 2024 16:25:33 +0000

Hi, I am simulating a microfluidic spiral channel. I have used the particle tracing feature and inputting 3 types of cells; Circulating Tumor Cells (CTC), Red Blood Cells (RBC) and White Blood Cells (RBC) according to their own particular size and density. CTC - 15 um - 1077 kg/m3 WBC - 10 um - 1080 kg/m3 RBC - 6 um - 1110 kg/m3

The results are well, showing the particle separating and eventually CTCs are separated from the RBCs and WBCs. Majority of CTCs ending up in outlet 1 while RBCs and WBCs end up in outlet 2. However, is there a proper way for me to tabulate a graph showing the types of cells and number of cells at the outlet? I do not want to tabulate the graph showing total number of cells as I want to distinguish between the number of CTCs, RBCs and WBCs at both outlets.

I have reviewed this blog: https://www.comsol.com/blogs/different-ways-to-count-particles-in-comsol-multiphysics/ But it shows methods to count total number of particles and not specifying the different particles.

Problem with RF Port Sweep

Fri, 10 May 2024 23:19:04 +0000

I am doing port sweep to export the SNP file. After the first port converges, for some reason the solver does switch to the next port. Please see the image attached. In a separate simulation file, I have activated each ports manually and the simulation works fine in that case.

Is it possible to use topology optimization to add additional material to a solid structure, rather than removing material?

Fri, 10 May 2024 11:53:51 +0000

Hello,

I'm trying to model a loudspeaker enclosure in 2D and use topology optimization to increase the low frequency response by adding additional material to the inside of the enclosure. My goal is a simplified version of this research article:

https://www.researchgate.net/publication/376153843_Loudspeaker_cabinet_design_by_topology_optimization

I've already simulated the initial design, but am having trouble with the optimization step. All of the tutorials I've found on topology optimization involve removal of material, not adding any additional material.

Attached are screenshots of my model and some of the results of the research paper for reference. I'm trying to add additional material to the orange fiberboard in the inner region which is occupied by air, similar to the paper. Any help or guidance would be much appreciated.

MUMPS error

Fri, 10 May 2024 05:58:56 +0000

Dear sir/ma'am, I am getting a warning "MUMPS memory allocation factor increased to 1.4399999999999999." while running the model.What does it mean and how to resolve it? Shall I increase MUMPS allocation factor? What should be its upper limit? Thanks and Regards

Questions about background reduced field in COMSOL Magnetic field module?

Fri, 10 May 2024 04:00:47 +0000

In the frequency domain research mode of COMSOL, we want to apply an AC magnetic field superimposed by a DC magnetic field, in which the AC field is applied through the coil. Can we regard it as a DC magnetic field by setting the background reduced field to a constant(In the two-dimensional axisymmetric model, the background field is set as the axial uniform magnetic flux density and is a constant) ? Or is the background reduced field a DC magnetic field or an AC magnetic field in the frequency domain? Thanks!

Ionic motion in dielectric substrate: structure alterations

Thu, 09 May 2024 20:43:23 +0000

Hi, I am simulating ionic migration in dielectric substrates under electric field. I am using electrostatic and transport of diluted species. Everything is fine up to this point.

When the positive ions move from the positive electrode to the negative, for glassy structures, I want to alter the structure left behind. Experimentally this is achieve by applying electric field and temperature. When the ions move, the structure changes in that region as one of the mechanisms of charge compensation.

How can I simulate this changes in structure?!

Thanks in advance!!!

CFD module

Thu, 09 May 2024 14:49:51 +0000

What is the difference between "slip" and "Navier slip" in the "wall" condition of a "laminar flow" module? As we all know, in microchannels, surface tension, EDL and other factors will affect the flow rate. How to couple multiple factors into the flow rate? In the wall setting, only one of the factors such as slip type and electroosmotic speed can be selected. Can all of them be coupled into a microchannel model? Could you please provide me with a detailed procedure or case? Thank you.

Precipitation and Evaporation in Porous Media settings

Thu, 09 May 2024 13:06:11 +0000

Hi!

I am currently modeling a 2D Porous media simulation in a coastal settings.

Here, I would like to simulate how salt content evolve overtime. I have the precipitation and evaporation data at the moment. However, I recall COMSOL does not allow inlet and outlet condition within one boundary (i.e., top soil layer).

are there any suggestions on this matter?

How to Obtain a 2D Projection Averaging Concentration Along the Z Axis?

Thu, 09 May 2024 11:11:08 +0000

Hello everyone,

I'm currently working on a simulation involving the mixing of two products within a microfluidic chip using COMSOL Multiphysics. I have successfully completed the simulation, but now I'm trying to generate a 2D projection of the average concentration in the XY plane by averaging values along the Z axis. This way, I can directly compare the simulated results with my experimental data.

The Challenges I'm Facing: I have tried using the Results section and the various Data Sets options, but I couldn't find a straightforward way to average the concentration data along the Z direction. I'm not sure how to set up a custom 2D Plot Group that can represent the average concentration.
What I'm Looking For: A method to generate a 2D plot that shows the average concentration values in the XY plane, averaged along the Z direction. Suggestions or advice on how to export these results in a format that can be compared with my experimental data. I'd greatly appreciate any insights or recommendations you could provide to help me visualize and export this 2D projection properly.

Thank you in advance for your help!

Best regards, Francesc

How to calculate the co and cross polarized transmittance/reflectance in Comsol?

Thu, 09 May 2024 04:27:11 +0000

In Comsol, I want to calculate the Txx(transmittance to x polarized for incident x polarized), Txy(transmittance to x polarized for incident y polarized), Rxx, Rxy, and so on in comsol. S21/S11 never gives info about the particular polarization, it gives the overall transmittance and reflectance. But how to find these components in COMSOL?