Latest Discussions - COMSOL Forums

How to Add AC Voltage

Fri, 26 Apr 2024 02:10:57 +0000

Hi all, I encountered some problems while using the current component in the AC/DC module, and I hope you can help me answer them. After adding an AC voltage with an amplitude of 5V to the model, the actual simulation result shows that the voltage amplitude is only 10^-7 power. I want to know what's going on. Or if you know how to add AC voltage, please let me know.

Thanks a lot.

How to use moving mesh to simulate an Electromechanics problem

Thu, 25 Apr 2024 14:47:32 +0000

Hi all

I meet a problem when want to solve a multiphysics problem when using solid mechanics and electrostatics.

I use 2D structure. And I have two parallel electrode, and there have two separate dielectrtic layer attached to each electrode, and the air is between them. If we apply the voltage to the electrode, then the two parallel electrode and dielectric layer will attach to each other until contact to contact to each other. I use moving mesh to simulate the moving of air between the electrode, because the electrostatic force have a relationship with volume of air. But I meet a problem, which is with the moving of two electrodes, the gap between two electrode is small, then the moving mesh of air domain cannot remesh, then the simulation is shut down. I want to know whether have a way to solve this problem? Or, whether there has a method to set the Contact criteria, if the gap reach a small value, then the software will assume this two plate have contact each other, stop the remshing and contract process.

Thanks a lot.

Best wishes, Jingcheng

FLow electrode capacitive deionization (FCDI) modeling, coupling of flow and electric fields

Thu, 25 Apr 2024 12:38:41 +0000

Hi all. I've been teaching myself COMSOL recently, and I'm trying to model flow electrode capacitive deionization, where a graphite collector plate on both sides applies a transverse DC voltage perpendicular to the graphite plate, and ions in the intermediate solution channel move directionally through ion exchange membranes on both sides to the flow electrode (a mixture of sodium chloride solution and activated carbon particles) in the presence of an electric field. I tried to simulate the flowing electrode (a mixture of sodium chloride solution and activated carbon particles) with a mixture model, and at the same time, following the example of electrodialysis in this case library, I used a cubic current distribution physical field to simulate the distribution of the electric field or the distribution of the degree of polarisation of the graphite collector plate in the case where the graphite collector is energised on both sides. The flow field simulation was successful, but unfortunately the electric field simulation calculations never converged. I wonder if I am overlooking some details or if I am choosing the right physical field. Any input on the above would be appreciated!

Failed initialization during second study step

Thu, 25 Apr 2024 12:34:27 +0000

Hi,

My model consists of two study steps. First, I apply certain boundary conditions in a stationary step. Then, I maintain these boundary conditions and apply an additional time-dependent load in a time-dependent study step. This used to work fine when modelling in 2D.

In 3D, both steps converge when run individually (i.e., a stationary study encompassing the boundary conditions and a time-dependent study without those boundary conditions but including the time-dependent load). However, when combining both study steps (i.e., applying the time-dependent load on the model that includes specific boundary conditions), I get the error during the initialization of the second step: * - Feature: Time-Dependent Solver 1 (sol1/t1) Failed to find consistent initial values. Last time step is not converged.*

I get the same error even when I don't change anything of the model during the time-dependent study step. It seems that the second study step is not (correctly) using the results of the stationary solver as initial values. Does someone know why this is the case and how I can solve the issue?

Thank you.

Using simultaneously a Parametric and a Function sweep

Thu, 25 Apr 2024 11:34:05 +0000

Hi, I am currently working on a model that I need to upload to a Cluster that has no MATLAB nor Javascript functioning, so everything must be contained in a .mph that i can run from CMD. I need to do several studies where a function and some parameters switch. If I have in my Study a parameter sweep and a Function sweep, the computation takes all possible combination beween these two sweeps. What I want instead, is to have studies done one to one.

As an example, if I have a parametric sweep with a parameter A taking the values (1,2) and a function sweep with (fun1(t),fun2(t)), what I want to be done is only 2 studies. One that takes [A=1,fun1(t)] and another one that takes [A=2,fun2(t)].

Thanks.

mass flux from rock matrix to fracture

Thu, 25 Apr 2024 07:30:45 +0000

Hello, everyone

I'm now doing TH coupling for a fractured geothermal reservoir. My model is very simple where a 2D surface (fracture) is emdedded in a 3D rock. What I want to do is to add a source term on the fracture (an interior boundary) indicating the mass flux from rock matrix to fracture. However I have no idea how to solve it.

Output in the result section

Wed, 24 Apr 2024 14:57:00 +0000

Hello Friends, I have a question. I would be grateful if anyone could help me I want to get an output, but I encountered a problem and I don't know how it is... In the data set section, I defined the maximum and minimum values and connected these two using join according to the formula I had (i.e. take the difference between the maximum and minimum temperature, divide it by the maximum value and give the percentage (data1-data2) )/data1*100 )) But I don't know how to get this output and show it now I would be grateful if any of my friends know how to guide me step by step. Thank you

Cohesive Zone Modeling only mode I

Wed, 24 Apr 2024 03:34:21 +0000

Hello,

I am modeling the connection of two objects using CZM (Cohesive Zone Modeling). I only want to utilize Mode I (tension) instead of Mixed Mode. Does anyone have any suggestions or tips?

Thank you.

heat transfer time transient analysis results are not smooth.

Wed, 24 Apr 2024 01:52:09 +0000

hello.

I am using COMSOL to perform a time dependent analysis and I am facing a situation where the resulting values over time do not converge (smooth continuous values).

The analysis is to calculate the temperature through Joule heating in a simple structure and I need to get a continuous and smooth value with respect to time. Even with a very small time interval, a few microseconds, the calculation shows a discontinuous change in slope at certain points as follows.

Is there any way to prevent this from happening with the time dependent solver option?

Thanks.

i uploaded (mash-deleted) model file. and you may check the graph image of transient temperature image from : ,,,

https://drive.google.com/file/d/1-1vwWjPE7z24-BxKagzqldwba9j11e3r/view?usp=sharing

,,,,

https://drive.google.com/file/d/1IhpdtN4fqCT-1m8jhsnLi8Z9ysAX_iRD/view?usp=sharing

Failed to find a solution

Tue, 23 Apr 2024 21:42:31 +0000

Hello Comsol,

I am trying to compute a model in electromagnetic waves, frequency domain. So, I have to find out two results, one with time modulation and other with without time modulation. When I simulated for without time modulation, I got the correct result and simulation working well. But, when I added time modulated equation in variables definition, I started getting errors. Initially, I got an error that the model is not converging, after I increased the number to iterations but as soon as I did that I get stuck in new error of singular matrix and returned is not converged. not all parameter steps returned.

I am attatching the model file with this message. Please let me know how can I reslove this issue.

Coupling Physics

Tue, 23 Apr 2024 16:58:13 +0000

Hi everyone,

How to couple the heat transfer in solids with the heat transfer in Porous media, as there are no options of multiphysic coupling. The interface between them is deined in the thermal insulation, however I want to simulate the heat transfer through this contact. I thought to define a heat source at the boundaries but I do not want to define a specific value, as I need to define the heat transfer from and to the heat transfer in solid in different scineraios.

If you have an idea, just say it. Thanks for your support

gear pumps

Tue, 23 Apr 2024 12:54:53 +0000

I am looking for anyone to share their experience with emulating gear pumps in COMSOL. I am looking for feedback on the modules used, the problem setup including. Boundary conditions, and solver configuration.

Coupling the Deformed Geometry (dg) interface with the Laminar Flow interface

Tue, 23 Apr 2024 11:01:36 +0000

Hi Could you please suggest a way for me of how to couple the Deformed Geometry (dg) interface with the Laminar Flow interface in 3D model?

Transient Simulation in COMSOL

Tue, 23 Apr 2024 10:35:08 +0000

Hello,

Is it possible to the transient simulation in COMSOL just by changing the source signal with different period? Without using the "Events" could we do transient?

Challenge: I am getting same rise and fall time for three different material in a single device. Lets's say in Silicon on Insulator, I am getting same transient effect for silicon as well as silicon dioxide.

Thanks

Phase initialization

Tue, 23 Apr 2024 01:22:04 +0000

Research background: My model involves transient calculations of many physical fields, including level sets and laminar flow. When using one research step for simultaneous calculation, the calculation step size is particularly small and slow. So I want to first calculate the remaining physical fields, and then import the results of each time step calculation into the horizontal set and laminar flow for calculation. Current issue: If the solution inherited from the previous research step is used to solve the transient, it will prompt that there is no inheritance initialization, resulting in non conservation of volume. If the phase initialization inherits the previous solution and then uses transient inheritance phase initialization, only the last step is inherited. Solution: 1. May I ask how to add a PDE module in a transient to achieve phase initialization? Is this idea feasible. 2. We are currently trying to import using COMSOL with Matlab. Or is there any other way?

Heat Transfer in Sand

Mon, 22 Apr 2024 15:47:52 +0000

Hello, I have experience in modeling heat transfer in porous media, but I'm now interested in simulating heat transfer characteristics within a soil matrix. Does COMSOL offer tools specifically for modeling heat transfer in soil or sand, or should I rely on custom material settings? For example, I want to conduct a 2D simulation for heating a thin layer of sand saturated with glue. I have all required parameters, I just need help in defining that the material is sand. Thank you for your time and consideration

very small timesteps in time dependent simulation

Mon, 22 Apr 2024 14:58:27 +0000

Dear all,

I am trying to do a mesh independence test on a time dependent Alkaline Water Electrolysis 2D simulation (Similar to the application libraries model). The physics involved are Euler Euler multiphase model and secondary current distribution. The file with the coarse mesh converges very quickly, but when I refine the mesh to check the mesh independence, the free time stepping starts taking very small timesteps after a certain time, and the simulation stalls with negligible progress. If I switch off multiphase, the model converges on both the meshes.So, I believe the non-linearity introduced by the Euler Euler model is causing this issue. I tried to check the model solution at this time for any signs of unphysical results/high residuals, but did not find any reason as to why the timestep size reduce. In the logs, I can see that the NLFAIL column increments before the time steps reduce, indicating the nonlinear solver is failing at the given timestep. The model possibly has a singularity at the junction point of the electrode and the insulating wall, which causes some oscillations in the electrolyte current density and disperse phase volume fraction, but even then the model converges at some conditions of inlet velocity, mesh size etc. I cannot pinpoint the exact reason for this behaviour. I had to clear all solutions due to size restrictions, please run the simulations to check the behaviour I described. Will be really grateful for any answers/suggestions, as I am new to comsol and attempting to solve this issue since more than a month. Please let me know in case any further info on this case is required.

Best Regards Amit

Initial stress values from stationary study not working as initial conditions for time dependent study

Sat, 20 Apr 2024 16:30:46 +0000

Hello!

I am currently using the Solid Mechanics module to simulate deformation of a shell over time. I have an initial stationary step were my material is originally very rigid, followed by a time dependent study of a much less rigid material (I use a smaller Young's Modulus).

I want to use the solution of the stationary study as an initial condition for my time dependent study. For this, I am setting the 'Initial values for the variables solved for' as the solution to my stationary study. However, when I plot the Von Mises stress for the first time step of my time dependent study, I'm not getting the same result as my stationary study.

Does anyone have any insights on why this might be, or any way to solve this problem?

Thank you so much!

How to export Electric Field map to TABLE file

Sat, 20 Apr 2024 15:33:38 +0000

Dear all, I'm a newbie in COMSOL. I want to use COMSOL to simulate the electric field and export results to input for Geant4 simulation. I need the output that has the format as below. I tried many ways to export the results but could not find any way I wanted. Can anyone help me, please? Thank you in advance.

        6           6          10

1 X
2 Y
3 Z
4 BX
5 BY
6 BZ
7 BMOD/HMOD
0 [METRE] -0.05 -0.05 -0.26 1.1283e-02 -4.3297e-03 -1.6583e-02 1.2566e-06
-0.05 -0.05 -0.22 2.4980e-02 -1.1691e-02 -3.9227e-02 1.2566e-06
-0.05 -0.05 -0.18 6.0657e-02 -4.1529e-02 -1.0921e-01 1.2566e-06
-0.05 -0.05 -0.14 1.9553e-01 -1.5685e-01 -2.8907e-01 1.2566e-06

Protein binding to porous matrix

Fri, 19 Apr 2024 18:10:44 +0000

Hi! I aim to model the binding (and unbinding as well) of protein molecules to a porous hydrogel matrix. But it seems there is no available module or function in the COMSOL. I could find a surface adsorption function, but my hydrogel matrix is a 3D domain and the protein solutes are inside the matrix, so I need a volumetric binding function to model it. Could you give me any comments? Thanks!