Latest Discussions - COMSOL Forums

sigst variable undefined

Fri, 26 Jul 2024 18:31:26 +0000

I am trying to study surface charge accumulation for a time-domain study on piezoelectric material. But, the sigst variable is always showing as undefined variable. The equation view is showing es.sigs0 is defined and has a value of 0 [initial surface charge density].

If the study is in frequency domain, then surface charge accumulation node works fine.

Thanks in advance.

Modelling an ultrasound wave (vibrations with fixed small amplitudes) in a membrane attached to an ultrasound transducer.

Fri, 26 Jul 2024 12:39:53 +0000

Hi all, I am fairly new to COMSOL Multiphysics and I am working on ultrasound transducers. An ultrasound transducer is fully attached to a circular membrane of certain thickness. The membrane is attached on the electrode of the transducer such that when there is a pulse voltage applied on the transducer and it displaces along its height it generates an ultrasound in the membrane connected. I am struggling to find a way to generate those vibrations in the membrane in my modelling. Can anyone suggest me how can I do that? Any advice/approach would be greatly appreciated as I am really stuck at this and am not able to find any document or material related to it. Thank you!

Inability to Add Boundary Conditions to Interior Boundaries

Thu, 25 Jul 2024 14:48:21 +0000

I have been struggling with how to apply interior boundary conditions to my model for the past several weeks. I went back to basics and drew an incredibly simplified model and added only one Physics node (Laminar Flow) to see if perhaps I had made a mistake while building my other model.

However, I am experiencing the same issue with this model.

I have read all the other discussion posts, and have tried using the assembly, makiing sure 'keep interior boundaries' is selected as well as using other Booleans and Partitions but no matter the settings I use, I am unable to select the interior boundary as it reads 'Inapplicable.' I suspect the Legacy Wall Feature might be to blame, but find I am still unable to select any interior boundaries as a Wall.

Any advice would be sincerely appreciated and thank you so much in advance.

Deep excavation by applying Hardening Soil Small

Thu, 25 Jul 2024 14:48:12 +0000

Dear all, I would like to model the deep excavation of the retaining wall using the elastoplastic soil model (HSS). I was wondering if, without using the activation in the linear elastic material physics (as the deep excavation tutorial does), any other method could be used to simulate the excavation. Thanks for your help!

Physics coupling between Turbulent Flow and acoustic calculation modules

Thu, 25 Jul 2024 11:18:26 +0000

I am currently working on a 2D-axisymmetric model on an aeroacoustics problem. I have done linearized potential flow study by the “Linearized Potential Flow” physics to acquire all the cut-on modes for different flow velocities. And I plan to follow-up with a calculation of the background mean flow by using the “Turbulent Flow, k-omega” physics. For the Multiphysics coupling, I found that only acoustics modules I can link are either Linearized Euler (L.E.E.) or Linearized Navier-Stokes (L.N.S.). Is possible that I can link the non-potential flow calculation (RANS) to a linearized potential flow solution through the Multiphysics option? If not, can I feed a modal type source to LEE solution as the source input in linearized potential flow calculation?

Thanks.

Transport of diluted species for high concentration

Thu, 25 Jul 2024 06:45:46 +0000

The 'Transport of diluted species' is used to study species transport when the solutes are in dilute form in the solvent. However, I want to model both the solute and the solvent together. How can I do so in one model when my solvent is at high concentration but I need to include it in the model.

Nanobubble Generator

Thu, 25 Jul 2024 02:24:46 +0000

Hi all, I am fairly new to the CFD module of Comsol, but I would like to be able to simulate a nanobubble generator nozzle. I have the CAD model to import (see attached image, although it is a slightly different iteration of the design,) but am not sure how to model the water flowing through it or test whether or not nanobubbles are created under certain conditions. Eventually, I want to be able to play around with the size and design of the generator itself and use Comsol to check that it still does in fact produce nanobubbles. Does anyone have any advice on how to go about doing this or any helpful resources? Is it even possible?

Thanks so much!

Strain Components in Cylindrical Coordinate System

Wed, 24 Jul 2024 16:14:44 +0000

Hi, I am applying a strip load on a cylindrical material and I would like to obtain the results of the strain components in cylindrical coordinates (r, phi, a) instead of Cartesian coordinates (x,y,z). The model of the material is linear elastic transversely isotropic.

Can someone help me to figure out how to plot the strain in cylindrical coordinates.

Thank you very much in advance.

Juan Martin Millan

heat transfer among fluid, solid and porous medium

Wed, 24 Jul 2024 13:36:36 +0000

Heat transfer occurs between a porous plate and a high-temperature fluid on the surface, and another gas is introduced to study the heat transfer in the porous plate. It is found that the temperature of the porous plate in the heat transfer of the porous plate is always at room temperature. How to couple the temperature of fluid solid heat transfer into it? The use of decomposition still cannot solve this problem.

Possible boundary condition for battery model

Wed, 24 Jul 2024 08:55:36 +0000

Hi all,

I am trying to model a battery discharge without any kind of constant current discharge or constant voltage discharge (i.e neither galvanostatic nor potentiostatic). Now, all battery models that I see in literature use either of these as a boundary condition. If i know no boundary conditions could you suggest where I should look or possible ideas for such a discharge behaviour. The external load resistance is the only constant, both voltage and current have to be solved by the model. Thanks in advance! Appreciate any help!

Battery Pack Design or Lumped Battery Interface?

Tue, 23 Jul 2024 17:55:53 +0000

Hi,

I have this BP Design 5s2p (See Image. I'll use symmetry to show the 2nd pack results) and I want to calculate the Battery Pack Life given the inputs. What interface should I use and Why? Is there any example model that may help me? Is there any advantages using the BP Design interface? Thanks in advance!

I have 6.0 version

How to continue the study after stopped using livelink for matlab?

Tue, 23 Jul 2024 09:32:56 +0000

Hi,

I am performing parameteric sweep using livelink for matlab.

Sometimes, I need to stop the calculation through the 'progress' window and assess the results so far.

Then, of course, I can continue the study by opening the comsol desktop --> study --> progress --> continue.

However, this way to continue the stopped study is not convenient bacause I have to open comsol desktop.

I was wondering if there was some matlab commands that can continue the stopped study without the need to open comsol desktop.

Best,

HC L

3D Carbon nanotube Tunneling

Tue, 23 Jul 2024 08:12:31 +0000

How is it possible to simulate the tunneling effect in a 3D Carbon nanotube for CNTFET sensor ? Thanks

"Java Exception" Problem During Multiple Iterations In Livelink For MATLAB

Tue, 23 Jul 2024 07:31:22 +0000

Hello, I'm having some problems with linking to matlab while downscaling a thermal stress model for comsol. Such as Java exception occurred: Exception.

com.comsol.util.exceptions.FlException: Invalid property value

Messages.

Invalid property value.

- Property: reconstructors

‘reconstructors’ as an array of strings.

- Stack trace: Array of alternating keys and values

Stack trace.

at com.comsol.nativeutil.properties.Property.C_(SourceFile:1308)

Property.C_(SourceFile:1308) at com.comsol.nativeutil.properties.b(SourceFile:1105)

at com.comsol.nativeutil.properties.eh.a(SourceFile:196)

at com.comsol.nativeutil.properties.f.set(SourceFile:157)

I would be grateful for an answer.

Guidance on which library (Physics) to use

Mon, 22 Jul 2024 21:42:38 +0000

Hello everyone, I have the following problem below.

"I need to simulate the pressure and velocity acoustic fields in two conditions: i) single hydrophone at the top of a 500 ml glass beaker; and ii) Two hydrophones installed on the side of the 2 m high tube assembly. Simulation must be a transient, to show the impact of the time between one pulse and another on the eventual overlap of the waves. Determining the minimum time between one pulse and another is important in the analysis. transmission mode, where the low transducer is immersed in the continuous medium. Consider that we have hydrophones with omnidirectional directivity that emit sound in the range of 70 to 110 kHz operating with pulsed waves."

-> My main question is the following: in Comsol, what type of library would I use to solve this type of problem and what type of tool available in the software could I use to simulate an analogue to the hydrophone?

Thank you very much for the answers in advance.

Lightning Strike on FFRP Plate Simulation

Sat, 20 Jul 2024 22:28:40 +0000

The objective is to obtain a numerical simulation of an experiment already performed in the laboratory. The test consists of replicating the impact of a lightning strike on a square composite plate

Based on various studies, the effects observed during a lightning strike include:

Thermal Effects:

Resistive Joule heating due to lightning current flow in electrically conducting structures
Direct heat input at the arc root area from the hot plasma channel

Transient Mechanical Force Effects:

Shock waves from the supersonic expansion of the lightning plasma channel
Magnetic volume forces due to impressed current flow in electrically conducting structures
Shock waves caused by exploding or vaporized materials (such as metallic foils, epoxy resin, and carbon fibers)

Considering my current setup, the only phenomena being replicated are the Joule Effect and the heating produced by the application of current.

With this in mind, what are COMSOL's capabilities regarding the other phenomena?

Which of these effects can be reproduced and coupled in COMSOL? Which modules should be used for these simulations?

Plotting the frequency vs displacement response for a mesh or node

Sat, 20 Jul 2024 06:45:54 +0000

Dear forum,

I am trying to simulate the frequecy responce of a piezoelectric device. It seems I was able to successfully set the piezoelectric properties, electrostatic conditions, and run the frequency domain study. Now I am trying to plot its frequency responce at certain positions using 1D plot (for example with respect to the center of one side of the piezo device), but I realized that I can only select the 'points' of the model. Is there any way I can slect a certain mesh or perhaps its node and plot its frequency response?

Thanks, new COMSOL user

Coupling different dimensions of PDE

Fri, 19 Jul 2024 11:13:48 +0000

Hi,

I have two coefficient form PDEs and two coefficient form boundry PDEs implemented in my model. But, in cofficient form PDEs dependent variable from boundry forms are marked as unkown function or operator. I have problem copling these pdes with different dimensions.

Thanks Maryam

How to suppress the 'Error in sweep' message and continue to execute the following code?

Fri, 19 Jul 2024 10:42:52 +0000

Hi, there!

I use livelink for matlab to preform parameter sweep. Through this code

model.batch('p1').set('err', false);

the 'stop if error' box is uncheck. Indeed, comsol will continue with the next parameter value if the current one encounters error.

However, when the parameter sweep is finished, comsol will pass all the error messages to matlab and stop matlab from executing the following post-process codes. Then, I have to execute these codes manually.

I was wondering if there was a way to protect the execution of matlab code from the disturbance of 'Error in sweep' message, so that matlab could running the following post-process codes automatically.

Best regards,

Temperature multiphysics field analysis

Fri, 19 Jul 2024 03:00:51 +0000

Hi！ The inclusion of a solid heat transfer module in the electromagnetic ultrasonic thickening analysis was unfortunately not possible to make the specimen non-isothermal after observing the temperature. I would like to know how to solve the problem of changing the temperature in the solid heat transfer so that the temperature of the specimen forms a non-isothermal domain. At the same time, when the temperature changes, the echo signal formed by the thickness measurement can also change with the temperature. A million thanks to all of you!