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

August 7, 2020, 5:30 am
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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:

  1. Get recognition for your research and development work

  2. Showcase your modeling and simulation expertise

  3. Connect with colleagues across industries and academia

  4. 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

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Saving accumulated probe table at time steps taken by solver?

August 7, 2020, 5:36 am
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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?

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Circular coil

August 7, 2020, 2:47 pm
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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!

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Rising air bubble in turbulent water environment (multiphase)

August 7, 2020, 4:01 pm
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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

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3D-shell

August 7, 2020, 11:39 pm
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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?

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Cluster sweep for a time-dependent study

August 9, 2020, 4:38 am
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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

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first Eigenmode not found

August 9, 2020, 7:03 am
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Hi everyone, I have problem in evaluating the eigenfrequency of a sinmple cantilever (one side fixed). I suppose to have problem in building a good mesh, the beam is composed of different layer with differend thikness (min thick: 0.2um, max thick:50um). When I use the eigenfrequency mode, the solution doesn t show the first eighenmode, which I evaluated experimenatlly. Can anyone help me to solve this issue? I can shear the file ... Thank you very much

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Diluted material transfer in fracture, d operators are not defined properly in the current context

August 9, 2020, 7:34 am
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Hello,everyone! Coulud anyone help me with this problem? Comosl is used to calculate the coupling problem of solid mechanical field and material transfer field. When no cracks were added in the material transfer field, it could be solved normally. However, when cracks were added in the mass transfer field, the following errors would occur. "d operators are not defined properly in the current context, please use dtang or average operators and d operators instead.- Expression: D (comp1.c,x) ' - I will apprecaite if anyone could help me with this problem!

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Two step stationary study, problem of using the result of 1st step as the initial value of the 2nd step

August 9, 2020, 9:11 am
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For this kind of initial value problem, there are lots of discussion over it. However, I still fail to figure out the way to do it.

Here is my simple test, I created one study including two stationary steps to figure out how this works. So I create a membrane fixed at four sides, which means when a pressure is applied on it, it could only deform in z- direction. In the first step, I apply a boundary load on it and disable another boundary load. In the second step, I disable the first boundary load and enable the second one. For the result, I can't see these two boundary load adds up on the membrane at the same time. I end up getting two seperate result from each step.

What I tried is to change the setting of "values of dependent variables", method:solution, study:study1, stationary. However, it still doens't work in my case.

Is there anyone knowing what setting i miss?

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Simulating the acoustic radiation force on a small particle in a viscoelastic fluid in frequency domain study

August 9, 2020, 12:39 pm
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Hi

I want to simulate the acoustic radiation force on a small spherical particle in a viscoelastic fluid by comsol multiphysics. I want to know, can I use the equations in this [https://www.comsol.com/model/flow-of-oldroyd-b-viscoelastic-fluid-4383] for the total stress to calculate the acoustic radiation force?

Tkank you.

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Extruding Circles

August 10, 2020, 1:15 am
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Dear COMOSL community,

I am new to COMSOL and am looking to extrude this design to make it 3-D but I feel I am struggeling more than i should be. The goal is to end up with a solid disc with many THROUGH holes through which air can pass during simulation and one could see the grid through the holes in the disc. So far when i extrude the holes or the enitre circle, all the mini holes still seem to keep their bottom or base - so they end up like a cave instead of a tunnel.. Ive tried this with all the mini holes being curved or solid - yet still to no avail.

ive spent a good amount of time on this only to feel like an idiot..Any help would be very much appreciated!

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Draw elliptical cylinder

August 10, 2020, 10:55 am
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Hello,

I am having problems drawing an elliptical cyllinder.

What is the equations for workplane?

Best.

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Intro to Simulating Optoelectronic Devices with COMSOL Multiphysics®

August 10, 2020, 10:56 am
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please can anyone share this .mph file discussed in this event https://www.comsol.com/video/intro-to-simulating-optoelectronic-devices-with-comsol-multiphysics-sep-19-2018

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What is the meaning of the variable of *ht.DeltaH*?

August 10, 2020, 6:42 pm
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When I studied the application* Concentric tube heat exchanger(Application Library path: Heat_Transfer_Module/Applications/concentric_tube_heat_exchanger, version: 5.4), I found a variable *ht.DeltaH in the expression of E (effectiveness of heat exchanger), which I couldn't find it in the Help document. What is the meaning of the variable ht.DeltaH ? Thanks for your help!

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Finding the amount of change

August 10, 2020, 8:12 pm
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I want to plot the "changes" of a domain variable (say temperature) between two different times in a transient simulation. for example the value of T(t=20)-T(t=10) in the whole domain. is there any way to do that?

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Adding 'for loop' and threshold limit

August 11, 2020, 1:59 am
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Hello Professionals!!!

I'm an intermediate user of comsol and need some hints and suggestions out of your experiences.

  1. I have to perform heat transfer simulations. The emperature of one cell (primary heat source) will increase with respect to time and the others (secondary heat source) will get affected resulting in the increase of temperature. I’ve to limit the increase in temperature of the secondary (for example 1000K) and make the temperature to jump from 1000K to 1500 K (in single step). How do I achieve this?
  2. How to add ‘for loop’ in comsol. for (i=0; a[i]>=800; i++) { a(i)=1400 }
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Zero Determinant of stiffness matrix

August 11, 2020, 7:50 am
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Hello,

I am trying to evaluate the conditioning of the stiffness matrix. My simulations work fine and seem to give good results. However, when I extract the stiffness matrix into Matlab using an assembly node and LiveLink, the determinant gives zero. Why does my simulation work fine, but the stiffness matrix seems non-invertible?

Thank you,

Alex

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Max/Min Volume Plot and Legend limits of Volume Plot

August 11, 2020, 8:38 am
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Hi, I am solving an electrothermal problem by incorporating the Electric currents(ec) and Heat transfer in solids(ht) Physics interfaces and the electromagnetic heating multiphysics coupling.

I have plotted the electric field norm(ec.normE) using volume plot as well as the Max/min volume plot. However, the maximum value of ec.normE displayed by the Max/min volume plot is greater than the maximum value of the volume plot legend. Ideally speaking, both values should be equal. What could be wrong here ? Thanking you in advance for any possible help..

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Limiting Dependent Variable

August 11, 2020, 10:44 am
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Hello I am trying to solve a system of PDE equations. Among the dependent variables of this system, there is a variable that changes from 0 to 1. I was wondering if I could do that in COMSOL?

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Friction Simulation

August 11, 2020, 3:28 pm
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I was wondering if anyone could help me with an issue I am having regarding the Friction node in Structural Mechanics.

I have a gold plate set on top of another. The top plate has an edge force applied to it. Enough force is set for the plate can be deflected by 100nm in the y direction (based on the orientation of the geometry). When my friction node values are set to default, with a mu value equal to 0, my simulation gives me that ~100nm deflection.

The problem I am having is that once the static friction coefficient value is set to anything that is not 0, as little as 1e-10, the change in the deflection is much greater than to be expecter. The deflection increases by at least a factor of 10.

Another issue occurs when I set the cohesion sliding resistence to any small values close to 0, the displacement values I get are ones that done math what I should have.

Thank you!

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