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Polarization rotation angle

May 10, 2017, 7:37 pm
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Dear all,

I am currently working on my bachelor project, which involves the numerical analysis of the feature of Metamaterials which can rotate the polarization angle of a linear polarized light that passes through it.I wonder how to calculate the polarization rotation angle.

For further understanding of my problem: Metamaterials are 2D or 3D structures which are usually arranged in repeating patterns in micron or nano scales. When a linearly polarized(along x axis) light incident to the Metamaterials, the polarization angle will rotate due to the coupling between the electromagnetic wave and the Metamaterials. In order to obtain the polarization rotation angle(θ) in frequency domain, I've tried two different methods with all the other setting are properly arranged:

1.Run a study in Frequency Domain(emw) and get the solution of x component and y component of the electric filed(emw.Ex and emw.Ex) on a certain surface near the exit port. Then use the equation: θ=atan(real(emw.Ex)/real(emw.Ey))*180/pi and get the polarization rotation angle(θ).

2.Build two ports(Port 2 and Port 3) as the exit ports, Port 2 only allows electric filed along x axis to pass through and Port 2 only allows electric filed along x axis to pass through. Run a study in Frequency Domain(emw) and get the S parameters (S21,S31). Then use the equation: θ=atan(S21/S31)*180/pi and get the polarization rotation angle(θ).

I wonder whether the methods above are correct or which is more reliable. If not, is there a better solution?please feel free to share your thoughts on this problem.

Thanks in advance.

Chuhuan Feng
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Torsion of a material with magnetic properties

May 10, 2017, 11:10 pm
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Good Morning,
I am a beginner with Comsol and I am working on AC/DC Module (magnetic field). I added a picture, where you can see two coils and a wire. In both there is current and around the wire there is a material which has magnetic properties. I would like to know the force and the torsion of that material. I do not know how I can set the calculation of the force, because it is not clear which domains and which parameters for the axis and the centre I have to set (I did not understand the equation which the software uses). I am interested in studying the torsion of the material. How can I see this effect also in 3D? Is it necessary a transient study? If yes how can I set this one?

Thank you for the kindness.
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Piezoelectric

May 11, 2017, 12:44 am
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Hi every one
i am using Piezoelectric devices module to study the effect of stress on a piezoelectric material but i have a problem.
an error occured when adding electric circuit eith resistor to load the resulting voltage ..
the error is attached

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ahmed
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Simple Question for Flow Rate

January 16, 2012, 10:30 am
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Hello,

I already done a few simulations with "laminar flow" using time dependent with rectangular input.

Input was "pressure, no viscous stress".

Is there any ways of getting the flow rate from "results" as post process?

I just calculated "area" * "velocity", but there should be a better way of getting it through Comsol.

Thanks.
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Flow rate calculation - 2D model - FSI

September 5, 2012, 5:45 pm
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I have a 2D fluid flow model with a flow through a channel with rectangular cross-section. There is one inlet with non-zero inlet pressure and outlet with zero pressure.


After solving, in order to compute the volume flow rate , I started by going to Definitions > Model Couplings > Integration. I created a integration for the outlet boundary (which corresponds to the height of the channel in 2D view) and named it intop1

Then I went to Study > Update Solution (I had already computed the solution), then I went to Results > 1D Plot Group, then 1D Plot Group > Global.

In the Global plot I added the expression, intop1(fsi.U)*W which gives me values in m^3/s....where W is a constant and is the width of the channel.


Can someone confirm that this is the correct way to calculate volume flow rate?

Thank you.
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How to generate Radially polarized light in wave optics module ?

September 12, 2015, 6:55 pm
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Hello

I want to generate radially polarized light in wave optics module. Can anyone help me ?
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MEMS Stresses and Strains

May 5, 2017, 2:00 am
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Hello,

I am relatively new to COMSOL and am trying to model a simple deformation of a MEMS bilayer. My geometry consists of a polyimide support (micro-meter dimensions) and a gold layer on top. I am constraining the polyimide (zero movement in y direction) on one side surface and applying a force on the opposite side surface (in the minus y direction). I am also applying a Roller boundary conditon on the two surfaces which are not orthogonal to the force. Due to the small dimensions of my model, I am obliged to choose a "finer" mesh.

I get the eror "Failed to find a solution. Out of memory during LU factorization. Returned solution is not converged."

I would be greatful for any suggestions that could make my model converge.

Thank you very much,
Amanda
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Plotting results along the curve

May 11, 2017, 4:59 am
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Hi,
I´m starting with Comsol and I need help. I want to plot results (stress) along the curve (but not line) so, that I have a 2D Graph - stress dependent on the curve. Thank for the help

--
sebik
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electric field distribution in composite materials

May 11, 2017, 6:09 am
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Hi
if anyone tells, how to build a model for composite materials
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thin film damping in frequency domain

May 11, 2017, 2:11 pm
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Hi
I'm simulating squeeze damping on cantilever. I use solid mechanics model and study in frequency domain perturbation. I add thin film damping and harmonic perturbation boundary load for cantilever, but the result is not correct, the quality factor calculated from resonance peak is too high, (comparing with experiment result) and there isn't distribution pressure on surface when i plot. So how to add the condition correctly and what conditions am i missing.
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Qn: Chemical reaction engineering module; setting viscosity of individual species

May 11, 2017, 6:27 pm
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I'm using the Chemical reaction engineering module to model fluid flows with the TCS transport of concentrated species interface. Or the RFCS interface, reacting flow in porous media. I am attempting to use the chemistry interface to calculate the gas mixture properties.

I'm trying to use the chemistry interface to calculate the gas mixture properties; Specifically, the mixture dynamic viscosity, in addition to the thermal conductviity and heat capacity..
I can see how to get the specific heat capacity, and thermal conductivity of the mixture: I can enter a value for the property of each species, and then the software combines them into an effective mixture value.

But it seems impossible to get the dynamic viscosity (of a gas mixture without a solvent) unless I want to employ the relationships from kinetic gas theory (pg 51 of the user guide). I have the dynamic viscosity data of each species, relatively constant.

I would like to go to the individual species nodes and enter a (numerical) value for the dynamic viscosity of each gaseous species, but the software doesn't seem to want to let me do that..

I can see the variables defined in the [equation view] Chemistry node:
Its "chem.eta_speciesname1" and Its "chem.eta_speciesname2"

But I just can't see how to change / edit them?? Why COMSOL is so intent to block me from doing this? I can't seem to enter a user-defined value for the dynamic viscosity of the individual species...
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How to enter mix type boundary condition in equation based modelling?

May 11, 2017, 10:30 pm
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I want to use "u=-du/dx at x=1" and "u=-du/dy at y=1". (d is here for partial diff, sorry about that).

How can I enter such type of boundary conditions in equation base modelling interface?

Any suggestions?

Thanks
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Pull-in voltage of resonator in 2D - keep getting inverted mesh elements

May 9, 2017, 5:54 am
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Hi,

I'm trying to find the pull-in voltage of a beam in 2D, essentially exactly as is done in the "Pull-in Voltage for a Biased Resonator-2D" model in the application gallery. The only differences are the dimensions (my bar is 100 nm thick, 15um wide) and the material (aluminium). I've tried different (types/sizes of) meshes but that doesn't help. The only thing that seems to help is to make the bar unrealistically thick (like 400 nm).

Usually I get an error something along the lines of "Maximum number of Newton iterations reached" , with a ton of inverted mesh elements in the warnings.

I'm pretty much out of ideas. All I want is to get the pull-in voltage but I don't know what I'm doing wrong. I've attached the simulation file.
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background field & extinction cross section with polarization

May 12, 2017, 3:39 am
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Hello. I am a user just started to learn COMSOL.
I have some basic questions, which I could not find answer in forum.
First, I am simulating particle surrounded in medium in scattered field mode, and with background field of exp(-j*ewfd.k0*z).
However, I heard that the background field should be exp(-j*k(in background material)*z) to correctly calculate scattering by particle.
However, if I'm using material from material library, I could not know the wavenumber in background field.
How can I set the correct background field in this case?

Second, I'm trying to simulate extinction cross section of the assymetric particle.
In this case, would the extinction cross section change through changing polarization?
If so, how can I calculate average extinction cross section, matched with experiments?

Any comments or discussions are welcome. Thanks in advance.
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Add microwave source to microstrip antena

May 12, 2017, 5:24 am
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Hello

I have a very easy model of microstrip antena (prntscr of model is attached) that i d like testing but i failed on add microwave port on it. I try add Lumped port (in real we have omega shape anthena where is microwave added by coaxial, but i d like make it very easy - input power is 1W).
But there is error

Uniform lumped port should be placed between two conductive boundaries.
- Feature: Type: Lumped Port
Tag: lport1
Operation: LumpedPort (lport1

Can you help me please?
Thanks
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How to simulate hologram in comsol?

May 12, 2017, 7:21 am
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Hi all,
i want to construct a hologram and want to get the object image in the result. Is it possible in comsol multiphysics? Can anyone suggest me which module should i use? and how would it be possible?


P.S- i want to construct a trapezoidal shape hologram which will be having four arms, and a hole in middle. The light will be inserting from the hole. The hologram 3D picture could be appearing at the plate which is placed at a distance from trapezoidal hologram.

Any suggestion would be appreciated!
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How to define Robin boundary conditions in a equation based modelling interface?

May 12, 2017, 7:37 pm
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I want to have these type of boundary conditions,

u=-du/dux, at x=1 and u=-a*du/duy, at y=1, where `a` is a parameter.

How can I input these conditions?

Thanks
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Implementing BCs for a travelling wave wall in Fsi

May 13, 2017, 12:30 am
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Hello,

I was a Fluent user till recently, but I needed more to couple multiple physics, still getting used to Comsol.
At the moment it's just Fsi.
For simplicity sake, I have 4 walls; an Inlet, an outlet, a fixed wall and an oscillating wall(shared wall with the material).
I am trying to have a travelling sine wave on this wall whilst fluid reacts to this oscillation.

I am wondering how should I do for a time dependent study, I have tried giving moving loads from the example peristaltic pump, and on another instance, using waveform and analytical expressions. I am not able tie up anything with Timestep and frequency of the travelling wave.

Are there any guides or another examples that I may have missed? Or, perhaps some can help directly, that would be grateful.
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Mesh element volume

July 1, 2009, 1:07 pm
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Dear all,

I have a material property having a different value in a domain and
it is function of individual volume of deformed mesh element and undeformed mesh
element.
Could you tell me how to get the volume of the mesh element?
In 2D, this may be the area of the each element. (Am I right?)

I appreciate your reply.

Thank you.

Yoon
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3D FinFET model

August 22, 2015, 6:41 am
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Dear COMSOL users
I have been trying to make a simple 3Dimensional FinFet model by using semiconductor module(comsol 5.0). After computing, I am getting the following errors. If you have any idea to find a solution, please let me know...

Undefined value found.
- Detail: Undefined value found in the equation residual vector.
There are 38 degrees of freedom giving NaN/Inf in the vector for the variable comp1.Ne.
at coordinates: (1.89791e-008,-4.70492e-008,-2.10694e-010), (1.88505e-008,-4.71681e-008,2.64803e-010), (2.51508e-008,-5.02182e-008,-5.59956e-009), (2.52283e-008,-4.98438e-008,-5.54877e-009), (2.37709e-008,-4.86442e-008,-1.69843e-010), ...
There are 30 degrees of freedom giving NaN/Inf in the vector for the variable comp1.Ph.
at coordinates: (1.89791e-008,-4.70492e-008,-2.10694e-010), (1.88505e-008,-4.71681e-008,2.64803e-010), (2.51508e-008,-5.02182e-008,-5.59956e-009), (2.52283e-008,-4.98438e-008,-5.54877e-009), (2.37709e-008,-4.86442e-008,-1.69843e-010), ...
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