Latest Discussions - COMSOL Forums

Points node numbering

Sat, 29 Jun 2024 01:44:59 +0000

Hello When creating points in geometry and try to assign them probes, the points numbering are not in order, so how can i make them in oreder because i am trying to create many points in the geometry and assign each on of them a probe and i am doing it through matlab livelink using for loop which i need the numbering to assign the probes accordingly. The for loop code is shown below and the numbering is show in the picture

i = 1; for theta = 0:45:359 n = ['pt' num2str(i)]; model.component('comp1').geom('geom1').create(n, 'Point'); model.component('comp1').geom('geom1').feature(n).label(['sensor at angle = ',num2str(n)]); model.component('comp1').geom('geom1').feature(n).setIndex('p', sind(theta), 0); model.component('comp1').geom('geom1').feature(n).setIndex('p', cosd(theta), 1); model.component('comp1').geom('geom1').runPre('fin');

model.component('comp1').probe.create(n, 'Point');
model.component('comp1').geom('geom1').run;
model.component('comp1').probe(n).selection.set([i]);
model.component('comp1').geom('geom1').run('fin');
i = i + 1;

end

Thank you

terminal velocity

Fri, 28 Jun 2024 23:32:13 +0000

Hi everyone,

I was wondering if it is possible to trace the instantaneous droplet velocity plot ?(?) for this tutorial: https://www.comsol.com/model/droplet-rising-through-a-suspension-90401 so that we can determine the terminal velocity.

How do I extrude 1-D variables to 2-D variables?

Fri, 28 Jun 2024 20:04:33 +0000

Lets say that I have the two layers. I have some 1-D variables at the interface of the layers, but for the display, I would like to show the 1-D variable not as a line but 2-D domain (like the bottom layer) underneath the interface (with the same x location).

I think this would not be very difficult but I cant find the way.

Thank you for your help in advance!

Best regards,

Assistance Needed for Simulating Dielectric and Mechanical Losses in SAW Devices

Fri, 28 Jun 2024 16:32:51 +0000

Hello everyone,

I am currently simulating a one-port SAW device in COMSOL, focusing on incorporating both dielectric and mechanical losses into the linear materials of Si and Mo, with Mo serving as the IDTs and Si as the substrate where the AlN film (piezoelectric) is deposited. Initially, I used the 'Damping' subnode for mechanical loss, setting it up as an isotropic loss factor, but I am unsure how to simulate dielectric loss. My questions are: (1) Is it correct to use 'Damping' as a form of mechanical loss? (2) Which subnode should be used for dielectric loss in the case of linear elastic material?

The images attached to this annex illustrate the physics nodes I am implementing in my model, along with the damping configuration for the linear elastic material as previously mentioned.

Thank you for your time and assistance.

T.M. Vieira

Porosity Gradient in a geometry

Fri, 28 Jun 2024 15:47:17 +0000

Hello, I am trying to model stress on a part that has a gradient of porosity; think a region of solid metal leading to more and more bubbles as a function of depth. Is it possible to add this to a geometry?

Simulation of Box type solar cooker using Comsol

Fri, 28 Jun 2024 04:41:05 +0000

How to simulate Box type solar cooker using Comsol

Does the comsol stress field that exceeds the range of the domain indicate deformation？

Thu, 27 Jun 2024 10:51:10 +0000

After calculation, if the stress field of the domain exceeds the original range of the domain, can I think that the domain has been deformed or expanded?

Band Gap Analysis of Photonic crystal

Thu, 27 Jun 2024 10:12:19 +0000

Hello everyone

I am new to COMSOL. I am working on a photonic crystal on the wave optics module. I took help of an example problem in COMSOL, where they simulated a GaAs rod photonic crystal. Since the refractive index of the GaAs Rod is frequency dependent, they have used an expression for the refractive index in the component1>defintion > analytic section for its bandgap analysis. Since I will be working with a material whose refractive index is constant across all frequencies, I changed the frequency expression to a constant value (the refractive index of the material). But in the study 2, I got an error saying: "Failed to find a solution for the initial parameter. Maximum number of Newton iterations reached. Returned solution is not converged. Not all parameter steps returned."

The pdf for the example of band gap analysis of COMSOL multiphysics is given below and also my simulation is attached below.

Please help me debug this

Thanks in advance Sankalp

How To Create A Coefficient That Depends On Water Content

Thu, 27 Jun 2024 07:48:49 +0000

Dear all,

I'm dealing with a 2 coupled PDE problem, related with diffusion of water in porous media, where the two variables are the temperature and the relative humidity.

I want to introduce a thermal conductivity which depends on the water content, k(w), but once I define it, it says that "I don't know what's w". I also defined w as an analytic function dependent on the relative humidity.

My question is: Can I define a coefficient that depends on a variable? (Apart from P or T)

Thanks a lot. Regards,

Heat Transfer Module - soil

Thu, 27 Jun 2024 07:47:39 +0000

Hello to everybody,

I am not an expert in comsol and I would like to know how can i make this performance:

A pipeline is intruded into the soil, and using the tube as a heat source, I would like to create a thermal diffusion analysis program that varies depending on the moisture content and thermal conductivity of the soil.

How can I make this model?

Thank you in advance. Best regards.

Error entitled "the DAE is structurally inconsistent"

Wed, 26 Jun 2024 23:37:06 +0000

Hello everyone,

I have a problem in my model, which is simulated in the RF time-dependent module. The error is "Errors when compiling equations. The DAE is structurally inconsistent." I think it is because of the boundary condition. I defined a uniform lumped port and connected it to the electrical circuit module. I would appreciate it if anyone took a look at my simulation file and helped me.

Finding inductance in meshed elements

Wed, 26 Jun 2024 13:56:32 +0000

Dear all, I am simulating the coil structure with predetermined mesh structure. after getting mesh, I need to find the impedance across each meshed element within the structure. Is it possible to do this??

I know, I have to excite before meshing but I want to find the impedace across each meshed element after meshing.

How to do this?? Please help me.

Here is the link for the sample mph file.

https://drive.google.com/file/d/1I8dTOGmuKW5hR8tNnixucAUHhU5bBKcb/view?usp=drivesdk

Microwave Resonator

Wed, 26 Jun 2024 10:12:22 +0000

Trying to model a superconducting microwave resonator. The model I have attached has the conducting plane material with a very high electrical conductivity (10^99 S/m). Also the Perfect electric boundary condition is used on those boundaries. In real world application, these selections might not be the best choice to model superconductivity as there might exist some Kinetic Inductance due to the Cooper pairs. For this I thought to add a complex valued electrical conductivity (purely imaginary, j/mu_0const(λ_L^2)2pifreq) to the material. So,

Just by adding a purely imaginary complex conductivity to the material instead of 10^99 S/m will be okay (PEC stays)?
If it requires that I add an impedance boundary condition (by replacing PEC, on the same boundaries), I am unable to do that as it is inside the vaccum block (the way it will be on a Printed Circuit Board in real world application). If I try to remove domain 2 from emw node, anything I try, I get errors that Uniform element 1 & 2 should be placed between two conductive boundaries.

I feel the ports are defined correctly and it is only the ways in which I choose to apply the conditions create the problem.

Please suggest any steps (which conditions on which boundaries) or any kind of modifications (geometrical) I can make to achieve it.

Study: emw study to observe S21 plot-resonant frequencies ,These are CPW lines

Solving Partial Element Equivalent Circuit (PEEC) formulation in COMSOL

Wed, 26 Jun 2024 06:09:39 +0000

Can anyone please tell me how to solve the Partial Element Equivalent Circuit (PEEC) formulation in COMSOL Multi-physics??

More on PEEC: The PEEC method represents complex 3D structures as interconnected equivalent circuits of basic elements. These elements include resistors, capacitors, and inductors, where each element corresponds to a physical segment of the structure.

In PEEC, we can compute Partial inductance, and AC resistance of any design.

3D nanomagnetic

Tue, 25 Jun 2024 22:45:36 +0000

Dear all, I do have a 2D model to study the magnetization dynamics induced by external current density applied normal to the surface that makes the magnetization rotating, however, when I extended it to 3D the simulation works but with a warning meesage; nonsymmatric matrix found and then ends up by saying singular matrix. i also plot the normal magnetization and found straigt lines for 2D while it is not for the 3D.

3D cylinder with spheres

Tue, 25 Jun 2024 22:19:20 +0000

Hello everyone, how's it going?

I would like to know how to construct a 3D geometry of a cylinder containing spheres formed into a tetrahedral shape. The height of the cylinder is 2 meters, with 50 mm diameters filled with 1 mm spheres up to approximately 1 m. Is there a way to do this in comsol?

Thanks.

4.2a Acoustic Streaming

Tue, 25 Jun 2024 13:33:48 +0000

Hello,

I am trying to create a simulation of the acoustic streaming in COMSOL v4.2a. As this is quite an old version, I cannot find much information on the subject.

I understand that first-order fields should be solved with a pressure acoustics or thermoacoustics interface, and then these fields should be implemented as source terms(?) in a laminar flow interface.

Actually carrying out this process seems complex.

Is anyone able to advise me on where I can find more detailed instructions on modelling the acoustic streaming in v4.2a, or would anyone have any model files that they would be willing to share with me.

With best regards, Peter

Extracting frequency dependent matrices (of a nonlinear eigenvalue problem)

Mon, 24 Jun 2024 15:40:09 +0000

The below post is related to an archived discussion

Hello,

I'm trying to extract (via Matlab LiveLink) the matrices from a nonlinear eigenvalue problem stemming from a physical model.

The stiffness and damping matrices of the problem are frequency dependent (as in the linked discussion), hence, I want to extract the matrices evaluated at a particular eigenvalue linearization point. Unfortunately, I'm not getting the correct matrices using the expect command:

mphmatrix(model,'sol1','out',{'K','E','D'},'complexfun','on','eigname','lambda', 'eigref',eigref)

(Solving the eigenvalue problem using the extracted matrices, does not give me the same results from the COMSOL solver)

I am missing some subtle detail?

Thanks in advance,

Filipe Soares

material

Mon, 24 Jun 2024 14:29:30 +0000

When I run “model.component("comp1").material("mat4").propertyGroup("def").func.set('source', 'file');”，there is an error：error use set ，and source is not a type of com.comsol.clientapi.impl.FunctionFeatureListClient.

How to calculate the area of change, e.g. ice in water

Mon, 24 Jun 2024 13:19:20 +0000

I want to calculate the change value of a changing area in a region, say a glass of water that is freezing, and I want to get the change value of ice, the difference between ice and water can be described by a phase field parameter (0 or 1), but it is not clear to me how to get the volume (or area, a 2D model) of the ice at each moment in time, and also how to get the rate of freezing (say the volume or area of ice per second). Any help would be appreciated!