## General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

#### How to

• Luca
Subscriber

Hi there, I am trying to simulating an acoustic device for acoustophoresis.

Someone can give me any advice to set workbench with the correct extensions?

(I am using Ansys 18.0 multiphysics, I have just installed the acoustics extension)

Thank you all.

• peteroznewman
Subscriber

Hi Luca,

I found a thesis on acoustophoresis. It had this graphic for the frequency range of interest in blue:

I did a "back of the envelope" calculation to scope out the maximum element size for acoustic models.

Assume your maximum frequency, f, is 10 MHz. The speed of sound, c, in water is about 1500 m/s.

Let's calculate the wavelength of a 10 MHz sound in water:  lambda = c/f  = 1500/10^7 = 0.00015 m or 0.15 mm.

At least 6 quadratic elements are needed along one wavelength to adequately represent the wave. That means the maximum element size in the model would be 0.025 mm for 10 MHz.

I hope your domain is very small if that is your maximum element size. If your domain is 5 cubic mm, then you will need 200 elements on a side or 8 million elements. That is a big model. If your domain is 10 cubic mm, then you will need 400 elements on a side or 64 million elements, which is not feasible.

You can redo the calculations for your maximum frequency, if it is < 1 MHz the model size becomes more reasonable.

Regards,

Peter

• Luca
Subscriber

My problem is before the setup of the problem or size of elements. In my workbench doesn't appear the harmonic response module. I tryed to download different module from the website,but probably not the right one.

If u could help me also in this "part" I will be very grateful.

Regards,

Luca

• peteroznewman
Subscriber

Luca,

Please send a screen snapshot of the Toolbox in ANSYS Workbench. I assume you are not using the Student license.

Does it show Static Structural? If so, then you are connected to a license server. The problem may be that your license does not include Harmonic Response. You will have to ask the license owner about that.

If the Toolbox is almost empty, then you are not connected to a license server. From Windows Start Menu > All Programs > ANSYS 18.0 > ANSYS Client Licensing > Client ANSYSLIC_ADMIN Utility. In that program, click Specify the License Server Machine, then Add Server Machine Spec and enter the Machine name and the port numbers. You have to ask the license owner for this info.

Regards,

Peter

• Luca
Subscriber

Dear Peter,

thanks for your answer, my toolbox is almost empty. I am linked to a server machine of Politecnico of Turin. I'm thinking that you are right, maybe my license does not allow Harmonic Response.

regards,

Luca

• peteroznewman
Subscriber

Dear Luca,

I was once on a license that only had Static Structural and Modal. Only after I upgraded my license did I get Transient Dynamics and Harmonic Response.

But if this is a Research license, I would be surprised if it did not have most of the licenses available.

Regards,

Peter

• Luca
Subscriber

This is my toolbox as you can see there isn't the harmonic response module

• peteroznewman
Subscriber

Dear Luca,

You have only installed the CFD tools, no Mechanical tools, so you can't use the Acoustics ACT as it requires the Mechanical APDL solver.

If your institution has Multiphysics, you should be able to run both.

Regards,

Peter

• Luca
Subscriber
Yes, i downloaded all the package, bit the toolbox is always like that.
We have an accademic research CFD license. So the mechanical tools are notte available.cdo you think that the only way to simulate acoustophoresis is to have Harmonix response module?
Regards Luca
• peteroznewman
Subscriber

A Fluent expert will have to comment on whether acoustophoresis can be simulated in that solver.

• Luca
Subscriber
I think none is going ti answer.
Thanks for all' your suggestions. If I'll fix the problem, I'll post the solution!
Luca
• Luigi0
Subscriber
it's been a while, but I want to to ask if you were able to model acoustic devices for acoustophoresis in ansys. I'm working on these, but I am in trouble.nThanksn
• MANUNAYAK
Subscriber
& ,nHope you guys are doing good!nRecently, I too have started working on Acoustophoresis. I'm just at the beginning stage. I'm referring to Prof. Henrik Bruss's publications as literature. Also I found few fellows have carried out easy simulation using COMSOL & Flow3D solvers. I'm looking for similar work, if any researchers have carried out using Ansys application.nLet me know, if you find any solutions.
• Luigi0
Subscriber
na lot of examples were carried out with comsol (Bruus et al.) and flow 3D, I only found an example using ansys fluent but the modeling process is not described in details (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6265899/). Personally I wanted to do a fluid-structure simulation (modeling also the piezo), but it is computationally too expensive because of separated timescale (vibrations of piezo and fluid flow) and I have problems.n Now I am trying to model the phenomenon only in fluent, simulating the vibrations of the piezo with a displacement boundary condition applied on a wall. Let me know if you have further advices because my simulations don't work properly.nn
• MANUNAYAK
Subscriber
nnThanks for your reply.nI will take a look into the link you shared. If I come across any progress, I'll definitely share with the community.nThanks!n
• Luigi0
Subscriber
see you soon here.nThanksn