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electrostatics(es)+transport of diluted species(tds) vs electrostatics with space charge density

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Hi,
Can anyone say why the 2 files give different results. I have used the analytical relationship of conc vs voltage in second file instead of tds module used in the first. Where have things gone wrong?

Best Regards
Anindita

Streaming potential-electrokinetics

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Hi,
Has anyone simulated streaming potential (electrokinetic flow in COMSOL)? I have been able to simulate electrosmotic flow(laminar flow, electrostatics, transport of diluted species), but not streaming potential. Should one use electric currents module? I have attached the electrosmotic flow module. A few hints on how to proceed would be very helpfil.

Best Regards
Anindita

henry constant

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hello
i want to design a membrane contactor wich i have to use qas liquid solution . the main problem i have is about gas concentration in interface .
how should i put henry constant in calculations ?

velocity profile

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greeting
I'm using the slip velocity for the wall condition and I got the following velocity profile
can any one explain why this decrease in velocity near the wall, please.

I1isoMax - mesh distortion

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Hi,

can anyone of you guys tell me how the 'I1isoMax' condition in Comsol is defined?
I'm using it for a simulation with large mesh deformation.
The only thing that I can find is that it is a condition for mesh distortion and that it shouldn't be 'above or equal to two'.
But how is it calculated or defined? And why shouldn't it be above two?

Would be great if anyone could help me.
(Proof with sources would be perfect)

Thanks a lot!
Stefan

Heat conduction in 2D model

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Hi, I am a beginner and I need help for a heat conduction simulation.
I have a 2D model of a hollow rectangular plastic case (thickness around 1mm) with a thin copper layer attached to one of the inner sides of the case. A heat source should be applied from the external environment and I want to evaluate the temperature response of the copper layer. Inside and outside the case there should be air (I don't know how to assign it because it is an empty space and i can't select it)
How should I proceed? How can I run the simulation?
Thanks in advance

How to setting "c" coefficient in Coefficient Form PDE

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Hi all
I am doing find the solution of PDE in COMSOL using Coefficient Form PDE. My PDE equation and its BCs described in my attached image file
My coordinate system in 2D, (X1 for horizontal axis, X2 for vertical axis)
u1: displacement in x1 direction [m], u1 is a function of X1 only.
rho = mass density [kg/m^3]
c66 is constant [N/m^2]

I setup the PDE coefficients like these:
da=alpha=gamma=beta=a=0
f=0
ea=rho

Dependent variables quantity: Displacement field(m)
Source term quantity: None

So my problem is that how to set "c" coefficient? Because in my PDE, it only has d^2(u1)/d(x2^2).
If anyone is free, please see my attached file and give a consultant.

Best regards

Problems to coupled "heat transfer in thin shells" and "electric currents, shell"

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Hello,

I am trying to couple "heat transfer in thin shells" and "electric currents, shell" to simulate Joule heating in a copper thin film where conduction, convection and radiation losses are not taking into account in the analysis.

The input current is 1 A and the thin film thickness is 2e-6 m, the problem is that the copper film is not heating up.

I hope you can give me some tips and help.

Regards,

Sergio

Saving the geometry file

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I am a beginner using COMSOL for practice I created a structure using geometry tool and saved it as.mph file but when I am trying to import the same model to analyse ,it is not showing the file in the saved path when I am browsing to import it. Could anyone please help me resolve this issue?

TTM Model with LTNE module

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Hi I was trying to implement TTM with the multiphysics called local thermal non equilibrium. The module is working . But how the equations given in heat transfer in solids and fluids related to LTNE multiphysics I did not understand. Means in the equation given which terms are coming from LTNE to hea ttransfer in solid and fluid.
Thank you

cell Reynold number

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Dear all,

I have some confusion regarding cell Reynold number option provided in COMSOL post-processing. What I understand is that cell Reynold number is calculated with velocity and length within/from a mesh element. Is it correct? If it is, it will show changes/different value of cell Re when i applied different mesh size, right?
So my question here is, what is the function/usage of cell Reynold number? or in what case it is normally applied?

Thanks a lot!

curved beam

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Hi,
How can I change the radius of curvature of a reinforced concrete straight beam inorder to come up with a curved beam?

what is emetric2?

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hi:

I am having trouble understanding a variable in CFD model. The cell Reynolds number is defined as:

spf.cellRe= 0.25*spf.rho*sqrt(emetric(u,v)/emetric2)/spf.mu

I realize spf.rho is sure the density of the fluid and spf.mu is the viscosity of the fluid, however, i cannot seem to understand nor find out what emetric(u,v) or emetric2 is. Can someone help me with this? thanks.

and yes i do know the defination of reynolds number. thanks.


Deposited Beam Power node under Heat Transfer module

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Hello,
Can anyone provide me with some example on how to use deposited beam power node under heat transfer in solids interface. I am trying to model a moving laser beam on a metallic plate.

Bending of cantilever beam

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Am a new user of Comsol 5.2a. My design is a fixed-free cantilever beam with a tip mass. I want to find the maximum thickness that can be given for a tip mass without the beam bending. Can anyone help me with the simulation?. Thanks in advance.

Joule heating using terminal

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Hello.
I'm trying to simulate the process of plasma-plasma sintering.
To set the heating rate, I model the PID controller with the input current at the upper boundary using the terminal.
But the resultant current at all points of the model is the same, which is incorrect.
What's my mistake?

I added a link to the model file, because I can not attach a file here.

yadi.sk/d/_DdnVw1t3McJo7

Fatigue module message "Stress cycle defined by stress amplitude "

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Hi, I'm using the fatigue module to evaluate the results from a solid mechanics object. However, I get the following warning message: "Stress cycle defined by stress amplitude 285686239.1227691 encountered. Fatigue cannot be evaluated ". I get a Cycles to Failure plot, but an area of the object appears empty.

Any ideas on what might be producing this warning?

I mighty upload the model later if required, the computer I'm using eighty now doesn't want to load the forum page, so I'm posting from my phone.

Thanks for any help,

Alfredo

How to obtain optical spectrum in Electromagnetic Wave, Frequency Domain.

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I am using EigenFrequency-Electromagnetic Wave, Frequency Domain in WaveOptics module to obtain the resonant frequencies of a resonator (a laser cold cavity).
Just wondering if possible and how to obtain the optical spectrum (wavelength vs intensity) based on the results I obtained in the module. Can I use the EigenWavelength (lambda) and Energy (ewfd.Weav) obtained from the simulations, respectively, as the x-axis and y-axis?

Many thanks!

Residual stress in Friction Stir Welding of Aluminium 6061-T6 alloy

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Hello Sir/Madam,

Actually, I have been working in a project "Simulation of Temperature and Residual Stresses in Friction Stir Welding of Aluminium 6061-T6 alloy. For this i'm using COMSOL 5.2a. i have gone through many journals and videos available online, but i'm unable to do the simulation for residual stresses.
Can you please help me. I would be very obliged to have your valuable suggestions.

Thank You.

Import Data and Interpolation

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Hello all,

I need to import data from an .txt file. I used an interpolation function, because it appears that it is the only way to do so. But interpolated data with a linear interpolation are not the same as the ones I wanted to import.

I work under COMSOL V5.2 on the acoustical/frequency domain study.
I need to import data : impedance = f(frequency)); and put them as a impedance boundary during my calculation. The calculation is done for frequencies in range(10,1,8000) and I need the impedance boundary value to change at each frequency step.

It appears that, because of the interpolation, my interpolated impedance values are not the same as the one I import.
I interpolated the impedance data from a table named imp.txt (which contains two columns "freq impedance") with a frequency step of 1Hz from 10Hz to 8000Hz :
10 4.23
11 5.48
12 6.45
...
8000 7.12
and used a linear interpolation and a constant extrapolation.
When I plot the imported data (in a table under Results tab, from the same imp.txt file) and the interpolated ones, the curves don't fit.

I don't know how the interpolation choose its own abscisses and it seems I can't control it ?

Thank you for your help !

Best,

Marie
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