Divergence VS Dimensions

March 26, 2014, 3:06 am

≫ Next: a few question about using COMSOL

≪ Previous: Parameter caculation

$

0

0

Good Morning,
I performed different simulations of flat coils to see the magnetic flux density without any error and results look reasonable.
The problem is that when I reduce the size of the flat coil (Diameter=30 [mm] , wire diameter=1 [mm]), and choose a finer mesh, Comsol fails to find a solution:

Failed to find a solution.
Divergence of the linear iterations.
Returned solution is not converged.

I am using Magnetic Fields physic. Should I use a different physic for very small devices?
Is the divergence because of the very small size?

Thanks,
Nima.

---

a few question about using COMSOL

April 4, 2014, 1:36 am

≫ Next: error meassages

≪ Previous: Divergence VS Dimensions

$

0

0

Hello, everyone,
I have a few questions to ask for your help,thanks in advance!
1. how to view the cross section of a 3D model? I wan to cut the model into two part and see the inside.
2. For the 1D plot, in the 'Expression evaluated for' , there are Harmonic perturbation, RMS for total solution. The plots are not same. Which one should I select to draw plot?
3. in far-field pressure , how to calculate the distance in COMSOL? I didn't understand it in help...
4. I set environment as the air domain and use PML. What's the differences between the cylinder domain and sphere domain?

I beg your help sincerely !

error meassages

April 9, 2014, 7:37 am

≫ Next: Is there some interface or boundary required to couple electromechanical and acoustic pressure modules?

≪ Previous: a few question about using COMSOL

$

0

0

Hi Mads,

I wish you could assist me with this error I am getting, when run the poroelastic wave model:

The following feature has encountered a problem:
Parameter list gives empty sweep
- Feature: Parametric 1 (sol1/s1/p1)
I expect it to be related to the mesh setting configuration.

Is there some interface or boundary required to couple electromechanical and acoustic pressure modules?

April 9, 2014, 11:45 pm

≫ Next: The pressure of the boundary probe is 0 ??

≪ Previous: error meassages

$

0

0

Hi everyone
I want to simulate a vibrating plant, and have a look at the pressure in air domain. Is there some interface or boundary required to couple electromechanical and acoustic pressure modules?

The pressure of the boundary probe is 0 ??

April 14, 2014, 4:01 am

≫ Next: liquid mixing using ultrasound (acoustic module)

≪ Previous: Is there some interface or boundary required to couple electromechanical and acoustic pressure modules?

$

0

0

Hi everyone
I simulate a vibrating membrane(or plate), I want to observe the pressure which is generated by the vibrating plate in the air. I set the boundary load in electromachenics and normal acceleration module and normal acceleration in pressure acoustic module to couple them. But I get the probe pressure on the plate 0 ?!
Could anybody tell where's wrong please??? Please help me!

liquid mixing using ultrasound (acoustic module)

March 25, 2012, 6:32 pm

≫ Next: Regarding Thermoacoustics

≪ Previous: The pressure of the boundary probe is 0 ??

$

0

0

Hi and good day for you

I'm new in Comsol, my question is, can I simulate the mixing of two immiscible liquid by means of ultrasound wave(20KHz and 500W)? how?
for example we have a small vessel (1 lit) containing two liquid (oil 50% and methanol 50%), I want to mix them using ultrasound wave(20KHz and 500W) and investigate the mixing time.
I'm unsure of which Physics modules to use and also how to couple them.
Is this even possible? Any help or advice would be great.

thank you so much
bahar sajjadi
PhD student

Regarding Thermoacoustics

April 15, 2014, 9:44 pm

≫ Next: Computing the kinetic energy

≪ Previous: liquid mixing using ultrasound (acoustic module)

$

0

0

Dear All,

I m new user to comsol Multiphysics..
I am studying Thermo-acoustis of tissues in a waveguide in Comsol 4.2..As a heat source i am usimng microwave(i.e. Electromagnetic wave(emw)) for my model..Also i am using BioHeat transfer physics....I have a few questions that arise in my mind...those are as follows:

1. What are the different physics required to simulate the geometry or get a thermo-acoustic signal ?
2. i have kept my tissue in water and water has high relative permittivity(epsilonr=77). I m not able to model the same and i am getting errors foe the same...how do i solve this ?
3. I dont need to use thermoacoustics for my model or can i use Pressure acouystics physics in my model
??
4. As a matter of fact i have made a pulse train of microwave power but i m confused about its arguments or you can say i am confused about the time(seconds/microseconds)..im not sure whether its working or not ??


please help...
Thank you in Advance

Regards,

Patil Abhishek Uday

Computing the kinetic energy

April 16, 2014, 10:58 am

≫ Next: Loudspeaker Modelling

≪ Previous: Regarding Thermoacoustics

$

0

0

Hi there,

When trying to compute the kinetic energy I am getting the following error message:

Failed to evaluate variable.
- Variable: material.rho
- Geometry: 1
- Domain: 2
Failed to evaluate variable.
- Variable: comp1.elw.rho
- Defined as: material.rho
Failed to evaluate variable.
- Variable: comp1.Ec
- Defined as: ((comp1.elw.rho*(((realdot(comp1.u,comp1.u)+realdot(comp1.v,comp1.v))+realdot(comp1.w,comp1.w))*0.25))*(comp1.elw.omega^2))
Failed to evaluate expression.
- Expression: real(comp1.Ec)
Failed to evaluate expression.
- Expression: real(comp1.Ec)

I have tried different way to evaluate the kinetic energy, but always getting the complaint about: the variable rho. I appreciate any assistance.

Thanks

---

Loudspeaker Modelling

March 6, 2014, 12:48 pm

≫ Next: Transurethral Focused ultrasound models

≪ Previous: Computing the kinetic energy

$

0

0

Hi, I have a simple cabinet with a port on the front face. I then have half a sphere normal to the front face acting as the air domain.

Firstly, how can I look at the modes inside the cabinet? Using the pressure acoustics module I have tried to link the air domain to the hollow space in the cabinet but it treats the whole model as air and the hard boundaries of the cabinet seem to be non existent.

Secondly, I want to look at the on-axis response. Is it possible to essentially place a microphone at a point in space in Comsol? I was thinking of modelling the woofer and tweeter as monopoles to begin with. Or is there a better way to approach this?

Thanks

Transurethral Focused ultrasound models

April 21, 2014, 4:44 pm

≫ Next: Acoustic Band Structure in 2d

≪ Previous: Loudspeaker Modelling

$

0

0

Has any one come across Comsol models on transurethral focused ultrasound applications? If so I could use some help. So far I have looked at other acoustic models which are similar but not quite like my problem. Please see the attached file for what the geometry looks like on Comsol.

The problem I am having is the acceleration boundary. I'm not sure I can define the normal acceleration for this geometry as the transducer is inside the tissue. Any help, will be appreciated.

Acoustic Band Structure in 2d

September 28, 2009, 9:51 am

≫ Next: solver problem

≪ Previous: Transurethral Focused ultrasound models

$

0

0

Hi Folks - Ive posted a couple of questions to some related discussion but it looks like they haven't been visited in a while so I thought I would make a new discussion group.

I am interested in finding out whether or not it is possible to calculate acoustic band structures using a reciprocal lattice simulation and periodic boundary conditions. I understand this is typically done by solving for eigan solutions to the helmholtz equation as you vary the direction of the plane wave vector. My question is... while performing an eigan value analysis and say, computing 100 eigan values in the vicinity of the stop band, how does one back out the wave vector direction related to the given eigan values

Thanks

Sean

solver problem

May 11, 2014, 10:31 am

≫ Next: Enforcing Sound hard boundary condition for interior boundaries - Acoustics module

≪ Previous: Acoustic Band Structure in 2d

$

0

0

Hello I have a problem with a simulation. I want to work on coda wave propagation. I think the problem condition and the mesh is correct but when I calculate after few hours I receive a message on the non-convergence of the temporal solver. I think I should maybe modifié something on the solver but I don't know what. Can somebody help me?

Enforcing Sound hard boundary condition for interior boundaries - Acoustics module

May 13, 2014, 10:29 pm

≫ Next: Design of CMUT

≪ Previous: solver problem

$

0

0

Hi,
Is it possible to enforce sound hard boundary condition on an interior boundary for a Pressure acoustics model? I can only find the sound soft boundary condition along with continuity and pressure.

Design of CMUT

May 20, 2014, 3:25 pm

≫ Next: Eigenfrequency Error "Cannot evaluate expression"

≪ Previous: Enforcing Sound hard boundary condition for interior boundaries - Acoustics module

$

0

0

Hai Saurabh, This is Sri. I hope you are doing good. I've been trying to design a Capacitive Micromachined Ultrasonic Transducer (CMUT) in comsol v4.3 But i'm unsuccessful. I've already designed many kinds of cmuts in INTELLISUITE but failed to efficiently design in comsol though i have almost 3 years experience on comsol s/w. I'll be more than happy if you can help me out in this issue. Thanks.

--
Sri Sairam Pasumarthi

Eigenfrequency Error "Cannot evaluate expression"

May 22, 2014, 1:21 pm

≫ Next: Measure the vibrations on the walls of a tank

≪ Previous: Design of CMUT

$

0

0

I am trying to compute the Eigenfrequency physics for a mesh I created and imported into COMSOL. The mesh is 3D, complex, and asymmetrical but I have had no problems computing with it in other studies. However, when I run the study I receive the following error:

"Cannot evaluate expression.
Failed to evaluate variable.
-Variable: comp1.acpr.p_t
-Geometry: 1
-Boundary: 1
Failed to evalulate expression.
-Expression: comp1.acpr.p_t
-Plot: surf1 (Surface)"

I suspect the error has to do with the fact I cannot select my mesh as the Sound Hard Boundary (Wall) 1. It says (not applicable) next to the mesh selection. Can I somehow create a boundary of the mesh to use for this? Is this why I am receiving the above error?

Thank you

---

Measure the vibrations on the walls of a tank

May 25, 2014, 10:12 am

≫ Next: Far Field Sound Pressure Level Plot

≪ Previous: Eigenfrequency Error "Cannot evaluate expression"

$

0

0

Hi
I am trying to build a cylinder with thickness 1.25mm and send an sinusoidal wave to it and plot the frequency response on the wall of the cylinder to the original frequency response. Kindly help me out with this and I am absolute beginner of COMSOL. So i am trying it difficult to build the cylinder with thickness and send some waves. Hope to hear from you.

Far Field Sound Pressure Level Plot

June 2, 2014, 11:11 am

≫ Next: About optical force calculation of particles manipulated by microring resonator

≪ Previous: Measure the vibrations on the walls of a tank

$

0

0

Hi there,
I was using COMSOL 4.3 to imitate the tonpilz transducer design that is easily accessible on the Internet. However, in the results, the far field sound pressure level plot generated automatically seems odd to me. It seems it has taken the magnitude of the sound pressure level at each point into the plot, so instead of a smooth spherical surface, it is rather bumpy and rugged. Does anyone know why this happens and how to fix this? I really appreciate it. Thanks.
Runkun

About optical force calculation of particles manipulated by microring resonator

April 23, 2012, 5:49 pm

≫ Next: How to find what "compute differential" documentation

≪ Previous: Far Field Sound Pressure Level Plot

$

0

0

Hi,everyone.

I want to simulate a structure which includes two bus waveguides and one microring resonator to form an on-chip optical tweezer. One microparticle is placed in the gap area between one waveguide and the resonator.

The structure is quite similar with:
pubs.acs.org/doi/abs/10.1021/nl100501d
(work from Kenneth Crozier, School of Engineering and Applied Sciences, Harvard University)

I want to use the Maxwell Stress Tensor method to calculate the optical force on it.

I tried the following:
In Results-Derived values. I added a surface integration for the whole surface of this ball-shaped particles. However, I am not sure how the expression of the force is.

If you have some ideas about optical force calculation, please feel free to discuss with me.

Thank you so much.

How to find what "compute differential" documentation

August 25, 2011, 9:55 am

≫ Next: Piezoelectric Study of waveguide

≪ Previous: About optical force calculation of particles manipulated by microring resonator

$

0

0

When I am plotting a Nyquist plot, I came across this option "Compute differential" under "Expression evaluated for:" option.

I just don't know what this means.

But instead of asking what it is, I want to know how am I supposed to find its documentation. I tried COMSOL user's guide, there is nothing told.

Can anyone help me on this?

Piezoelectric Study of waveguide

June 9, 2014, 10:11 pm

≫ Next: PLZ NEED HELP !!! Failed to evaluate variables

≪ Previous: How to find what "compute differential" documentation

$

0

0

Hello.

I have made a model of lithium niobate waveguide cladded with silicon dioxide. As lithium niobate is a piezoelectric material I intend to check the inverse piezoeffect caused by my input signal in the waveguide.

To this end I added study of "Electromagnetic Wave, Frequency Domain" from RF module and "Acoustic-Piezoelectric Interaction" from Acoustics Module.

But unfortunately I am getting an error: "Segregated solver steps do not involve all components."
Can anyone help me with this? Secondly, is "Acoustic-Piezoelectric Interaction" from Acoustics Module good for this task or should I be using some other study from some other module? Say, "Piezoelectric Devices" from structural Mechanics module.