Acoustics Module - Latest Discussions - COMSOL Forums

Simple Acoustic

Tue, 15 May 2012 07:53:45 +0000

Hello,

I am trying to model a 2D acoustic time harmonic square (10x10[m]; left bottom corner at (0,0)).
At the top the pressure is 101325[Pa] and now I just wanted to get started with the gravity force as a kind of a load, but how can I implementate it to get a continous rise of the pressure?

The 2nd step should be to create a point-source which is located at (0,0). But this is as well unknown for me yet.

Thanks for any hints on this.
Nikolaus

How to use multiple parameter to generate the desire probe plots

Sun, 06 May 2012 14:36:58 +0000

Hello everyone,

Does anyone know how to get the desired graphs axis from the table when using a continuation parameter and auxiliary sweep, study 1 and 2 respectively?

Initially the probe plots (9total) is a 3 spikes (acceleration vs. number of values computed consecutively for each corresponding user-defined internal pressures). I've chosen 0 300 600 psi, respectively.
When running the Pre-stress (study1) and then Frequency Domain (study2) the Result tab shows a generated tables values with accelerations (i#) for the 9 probes mounted onto the shell, evaluated over a frequency 16905-16920 Hz, step size 0.25. When the calculations are re-run the 3spikes now has a different x axis replaced with ExtPressure, not 0-123 steps (41 for each pressure defined), which is the consecutive sum of the frequency range/step size for each pressure evaluated. The issue may be a Parameter problem. Both desire 3-peaks and the generated plots w/ x-axis EXTPressure have the same Table values, just different representation.

How can I get Comsol to generate the initial 3 spikes with the # of evaluated steps on the x-axis for different external pressure say: 0 100 600 psi every time we compute study 1 & 2 is re-computed from initial file state?
I ignore the irrelevant study 3 (eigenvalues) .
See attached problem file and Pictures of the two desired probe plots with the right x-axis.

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Arts, crafts and sciences uplift the world of being and are conducive to its exaltation.
~Baha'u'llah

loss factor

Sat, 05 May 2012 06:29:29 +0000

Hi,

Is the loss factor in COMSOl the same with the viscosity factor?
I got the viscosity factor of silicon( as in the attachment) . And i want to use thest datas to calculate the Q factor of a MEMS resonator.

How can I do it? Can I directly consider the datas as loss factor in comsol?
Thanks!

Jun

iterative mesh

Fri, 04 May 2012 04:03:44 +0000

hi,
I tried to simulate a pressure reflection at acoustic pressure model.
when I build the mesh definitions i got "out of memory" error
I know there is an option to do iterative mesh / or to define an iterative solution that automatically considering
an iterative mesh until the wanted mesh.

HOW I DO THIS AT PRESSURE ACOUSTICS?

thank you

Dear Dewar

Mon, 23 Apr 2012 11:06:40 +0000

Dear Dewar ,

I saw your message on the forum and I'm writting you right now because I'm working on the same example.
I have a piezoelectric device which excited with a transient voltage and look for the admittance and displacement. I did the same with " Frequency Domain " it works very good ! But I'm now I'm trying to do the same with " Time Dependant " with a transient voltage , but I don't know how can I insert a transient voltage in my problem. I saw on your model you added a " Rectangle 1 " in " Global Definitions " it's he idea , but I don't know how did you use that after ?

If you have any question about " Frequency Domain " don't hesitate to send me an email.

Best regards.

Omar.

Baw Resonator Problem

Thu, 19 Apr 2012 10:03:41 +0000

Hi
I am working on a baw resonator. For our simulation we have considered a 3.5a COMSOL 2D model of Thin Film Bulk Acoustic Wave Resonator in the model archives of COMSOL.

So we treid to simulate the 3d model in 4.2 but so far we are not able to achieve any displacement and correct results.We were struggling with the meshing earlier but we adopted swept mesh with tri and tetra for our model.

Our Model consist of 4 thin layers of diferent materials and we want to obtain freq. response on the aplication of the voltage.

Please inform us about the ambiguities and errors in our model so that we can conclude our research.

Thank You
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Vineet Bansal
Project Associate, NPMASS
Electronic Science Department
Kurukshetra University, Haryana

thermo-acoustics velocity question

Tue, 17 Apr 2012 13:37:18 +0000

I'm new to COMSOL so please excuse the simplicity of this question. I'm using the thermo-acoustics module on a 2D axisymetric cylindrical tube. I want to determine the volume velocity at both ends of the tube given a known pressure boundary conditions. I see that there are two velocities I could use. One is the instantaneous velocity ('ta.v_inst') and the other is the z-component of the velocity ('w'). I did a line integral on the revolved 2D data set for both but the results differed. What's the difference is between these two variables?

Green function

Mon, 16 Apr 2012 09:25:10 +0000

Hi Comsol users ,

I want to calculate the radiated pressure at any point on a surface ( S ).
For that I need the Green function G(R,r) solution of the Helmholz equation.

I want to know if this function exists on Comsol 4.2a and how can we use it ?

Thank you.

why does pressure apply follow the z-axis in 2D space dimension?

Thu, 12 Apr 2012 23:14:45 +0000

Good day everyone.
i am using comsol 4.0a : 2D, geometry is rectangle and polygon, material is water, pressure acoustic, when i applied pressure for polygon, it will be followed z direction which is i dont want to happen.
like my figure in the attach file
please help me.

Acoustic Module Simulation

Thu, 12 Apr 2012 16:49:08 +0000

I am just wondering what would cause the damping effect on fluid-structure interaction simulation based on Acoustic and Structure modules. For instance if you run two simulations, one on air and the other on water. You'd see the higher damping effect from frequency response. You can even calculate the damping using Half Power Bandwidth Mehtod. When I run fluid-structure interaction simulation using Acoustic module without adding any damping, I could still see the extra damping effect of water compared to that of air. What caused this? Thanks!

air acoustic pressure quesiton

Mon, 09 Apr 2012 12:25:22 +0000

Hi:
I am a new starter.
I am studying the air pressure question on a thin plate (8cm*1cm*0.04cm) in a sealed chamber. The plate is fixed in its middle portion on the bottom of the chamber by a double edged tapes. And I would like to focus on the quasi-static frequency (<10 Hz).
I am wondering which mode I should choose. Acoustic shell interaction-frequency domain or acoustic solid interaction-frequency domain. And a key question is how to set the boundary condition?

Thank you!

Ying

Ultrasonic Stimulations

Sat, 07 Apr 2012 12:00:30 +0000

Hi,

I amusing the COMSOL 4.0 acoustic module for my simulations on ultrasonic waves. Specifically I need the pressure and temperature distributions resulting from the application of ultrasonic waves for a defined time.
In addition, I would also need to know whether it is possible to define a port as the ultrasonic waves (in the same way as it is defined in microwave oven model)?

Any of the help to help resolve the issues will be highly appreciated.

Thanks in advance.

Export Audio File from Comsol 4.2

Sat, 31 Mar 2012 23:58:24 +0000

Dear all,

I'm new to comsol. I'm wondering if someone can please tell me if there is anyway to export acoustic transient analysis results to an audio file in Comsol? If so, how do I go about it?

Thanks,

anne

Time convergence issue

Tue, 27 Mar 2012 07:26:42 +0000

Hi

Im working in the acoustic domain for quite some time.
Im using the time dependent model for simulation (generalized alpha).

The log file is attached below .
I cant understand what the out refers to in this case.
I occurs randomly at fixed intervals

The range(0,0.5e-7,24e-6) is used at the times field for time dependent study .
The time stepping is 5e-9.

How do i check for whether the data is converging or not?
How should the convergence plots look ?
Help in any kind will be really really useful.
Thanks a lot for your time and effort!!

Ive attached the snap shot of the time dependent study and the log file.

Regards
Glenston

How to set a material's density is anisotropic ?

Mon, 26 Mar 2012 12:04:37 +0000

hi, I'm new in comsol
I'm trying to define a material ,but its density is anisotropic , I don't know how to do with it.
could anybody please help me with this?

liquid mixing using ultrasound (acoustic module)

Mon, 26 Mar 2012 01:32:27 +0000

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

comsol microphone simulation

Wed, 21 Mar 2012 12:45:36 +0000

Hello experts
I am a beginner in comsol, so I would like to ask you some question about the microphone. I have a membrane radius is 143um, as well as the membrane thickness is 5.5um microphone, and I key the value into parameter, but the comsol can't run out of results to my problem, so I ask which side got a problem? thank you.

P.S I use an example of the comsol built-in microphone

How to evaluate a vector integral using Comsol

Tue, 15 Nov 2011 03:44:27 +0000

Hi:
I want to evaluate the integral of Xdx+Ydy+Zdz, which is a vector integral. However, I'm not sure if the line integral in Comsol is evaluating a scalar integral or not. Could someone let me know how to evaluate a vector integral?
Thanks a lot!

Is there any model about anchor damping in COMSOL?

Tue, 25 Oct 2011 06:19:21 +0000

Hi everyone

I am a beginner in COMSOL and I want to calculte the anchor-loss-limited Q in MEMS resonator (square plate resonator which has four anchors at its four corners). I think the perfectly matched layers (PMLs) should be used to absorp the outgoing elastic energy. Could anyone share a model about anchor damping? Thanks.

James

how to interface a piezoelectric device with an electrical circuit ?

Mon, 25 Apr 2011 15:19:33 +0000

I'm just discovering COMSOL. I have built a FEM model for a piezoelectric device and could successfully compute its electrical impedance, etc..

Now I want to drive this piezoelectric device through an electrical circuit. I have added an 'electric circuit model' to represent this circuit. The circuit is very basic and contains a ground (terminal 0), voltage source (terminal 1 0) and resistor (terminal 1 2).

How can I specify that the terminal "2" of the electric circuit is connected to the signal electrode of the piezoelectric device and terminal "0" to the ground electrode, so that the piezoelectric device model and the electric circuit models can be combined ?

In the 'piezoelectric device model', it seems that it is possible to specify 'Circuit' as Terminal Type. I've tried to specify the same terminal number "2" as defined in the electrical circuit but it does not work. How should I do ? Should the terminal number be specified in a different way ?

Thanks for your help.