## General Mechanical

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

#### Resonating a body using sinusoidal acoustic wave

• Hassan.liaquat
Subscriber

Hi there;

I am trying to resonate with a submerged body using sinusoidal acoustic waves.

Please correct me if I am using the correct way. Using modal analysis, I made a body and gave it the properties of the liquid. Within that body, I modelled a solid body (of which natural frequency was to be determined). I defined frictionless contact between them-No separation.

The liquid was constrained from all sides, and the solid body was constrained at a point to determine the natural frequency. I did get some values for natural frequency, and I decided to use the participation factor to select the favourable mode.

Now should I model similarly in harmonic acoustics? Define that liquid body as the acoustic region and the solid as the physics region (Structural).  I have to add the design of a transducer (sound source too).

And give that natural frequency as an excitation frequency to the acoustic source?

• Erik Kostson
Ansys Employee

HI

We can do that using the coupled field harmonic system in Workbench – you can have structural (structurak region), piezo, and acoustic (fluid) regions together there. It is always best to share topology between parts (or mult-body part in design modeler) in order to avoid contacts.

Yo would drive the piezo at the resonance or you can sweep the applied sinusoidal voltage from frequency to an end frequency.

Unfortunetaly we do not have tutorials on this, but see below and the internet:

See example td-53 in the help manual.

(do the same but in the coupled field harmonic system)

All the best

Erik

• Hassan.liaquat
Subscriber

I am making a minor correction in my question, a mistake due to auto-correct.

"I am trying to excite a submerged body using sinusoidal acoustic waves."

The video you shared tells about how to make a transducer and give it excitation within an acoustic region. i have few questions more:

1. I never knew that the "Harmonic response" module gives options for acoustical studies. I thought I should use Harmonic acoustic, isn't it? What's the difference between them if the harmonic response also allows acoustic excitation and acoustic region?

2. I want to focus these waves from the transducer (Focused transducer) to excite a body, let's say, a spherical body submerged in an acoustic region (Let's say water), to be excited by these waves.  This video shows the disturbance within the acoustic region due to acoustic waves from the transducer, but it does not show how to target a body with these waves. Can you please guide me further

• Erik Kostson
Ansys Employee

Hi

1. This is an old release using the old act extensions, I just wanted you to see the workflow inside mechanical (boundary conditions, etc). Thus the way to do what you want in the current releases is by using the Coupled Field Harmonic system in Workbench – you can have structural (structural region), piezo, and acoustic (fluid) regions together there.
2. As we said in the coupled field harmonic system we can have structural (structural region), piezo, and acoustic (fluid) regions together there. The spherical submerged body would be a structural region inside the fluid (acoustic region). Again it is best to share topology between all regions (so to get a connected mesh between them) and avoid contacts.

All the best

Erik

• Hassan.liaquat
Subscriber

Hi Eirk

I did try coupled field harmonic. I have defined the structural region but cannot define the acoustic region. Please see the image below. The purple region is the fluid domain. I selected to define it as an acoustic region, but it's not accept it.

It's a 2D model. Purple region is Fluid (water-liquid material), and this curved surface is a piezoelectric transducer immersed in the fluid.

I am using a licensed academic version of Auckland Uni. of Technology.

• Erik Kostson
Ansys Employee

Hi

Two things here to start.

1. We can not have 2D geometry in harmonic acoustics or coupled field harmonic – so these systems are only for 3D analysis and thus need a 3D geometry.
2. Set the material to water or air for acoustic domain and say steel (or material as needed) for structural under the geometry before defining the physics regions

All the best

Erik

• Hassan.liaquat
Subscriber