How to

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  • Last Post 28 June 2018
Luca posted this 25 June 2018

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.

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peteroznewman posted this 25 June 2018

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 posted this 26 June 2018

Thanks Peter for your answer. And thanks for your advices.

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 posted this 26 June 2018

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

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Luca posted this 26 June 2018

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 posted this 26 June 2018

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 posted this 27 June 2018

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

 

peteroznewman posted this 27 June 2018

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.

When I download ANSYS, I can choose Structures or Fluids. Can you go and download and install the Structures components? 

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

Regards,

Peter

Luca posted this 27 June 2018

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 posted this 28 June 2018

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

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Luca posted this 28 June 2018

I think none is going ti answer. Thanks for all' your suggestions. If I'll fix the problem, I'll post the solution! Luca

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