Hi,
when I simulate the 1-3 piezoelectric composite transducer, the generated acoustic field is nonuniform. the acoustic field picture is attached, I want to know why？
Hi Giordano,
Thank you for your good explanation. I think when the transducer is work in high frequency, the near field is nonuniform, am I right? so the acoustic picture is the reality condition.
In any realistic medium, there is attenuation of the wave, also there is dispersion of the wave, nonlinearity is there as well. In your figure, I guess those distinct features are higher modes, or nodes-antinode formation. Or, most probably they are array signature! Read about mainlobes and sidelobes and field pattern!
It can be due to numerical simplifications in the vicinity of boundaries in case of FEM simulations, especially if you consider absorbing boundary condition.
Hi Maysam,
I am not sure " numerical simplifications in the vicinity of boundaries", you mean the setting parameters in the perfectly matching layer or something else？
Thank you for your attention!
As far as I understood you have made an FEM model with piezo composite transducer and a media (probably water?!) on top. You are exciting the transducer and looking at pressure field in water. Correct me if I am wrong. on the boundaries of your model, I mean on the sides of your media, the boundary conditions are very important. Any boundary condition (even absorbing boundary) will generate some reflection which affect the beam.The numerical errors accumulates on the boundaries which may change your beam. On the other hand, if you are not using a symmetry model, even if the geometry has symmetricity by itself you may not receive a symmetric beam profile, and I think that can also be due to the size of elements in different parts and again numerical errors.
The model is exactly as you describe, I can not agree you more. and I want to know usually how to judge we have set a correct boundary conditions, such as absorbing boundary, Thank you!
Just do not forget that absorbing boundary in the software is never ideal, you have some minor reflections which may affect your beam. It took a lot of time from me to realize.
Dear Chunying,
What size and shape is your transducer? What is its centre frequency and bandwidth? What drive signal are you using (e.g. pulse, tone burst, continuous wave)? How far away from the transducer surface are your plotted results - are they in the near-field or far-field region? All of this information will help interpretation of your model results.
The acoustic field generated by a transducer will never be uniform. This is due to the acoustic wave from different parts of the transducer interacting through constructive and destructive interference at different locations in the material. Assuming the material the sound is propagating in is isotropic, the main variables that effect the acoustic field are:
1) size and shape of the transducer surface
2) velocity of sound in the material
3) wavelength of sound generated / natural frequency of the transducer
4) bandwidth of the transducer
The equations that describe the acoustic field are identical to the equations that describe optical diffraction. Have a look at the links below, they show all you need to know to be able to model the field yourself.
Hope this helps.
http://www.mathpages.com/home/kmath242/kmath242.htm
https://amath.colorado.edu/faculty/beylkin/papers/LE-BE-MO-2013net.pdf
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