II. How To Use ATILA

6.3 Tonpilz Sonar (4)
PROBLEM TYPE


PROBLEM - Tonpilz Transducer under Water, Axisymmetry, PZT8, Steel and Aluminum


PROBLEM TYPE - Modal Analysis

Data -> Problem data -> 2D, Axisymmetric

Make sure Geometry is set to 2D, and that the model Class is set to Axisymmetric. Next, change the Analysis to Harmonic, and check both Compute Stress and Include Losses boxes.

Finally, make sure the Mesh Units are set to millimeters.

Do not forget to validate your changes by clicking on Accept Data.

Frequency Intervals

The harmonic analysis is performed for frequency intervals that we must specify. Open the Frequency Intervals window, and define a linear frequency sweep between 25 and 55kHz with increments of 1kHz.

Next, create a second interval (by copying the first one), and define a frequency interval between 32 and 34kHz with increments of 100Hz.


 

 

Click on Accept Data to validate your changes.

Repeat for a third interval between 36 and 40kHz with increments of 200Hz.

The choice of intervals is dictated by the user's knowledge of the system and desired objectives of the analysis. Here, we use intervals 2 and 3 to obtain a smoother admittance plot around the electrical resonance and antiresonance of the transducer.

The frequency intervals are automatically combined and sorted. The list of frequencies that will be used for the harmonic computation is:
 
25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 32100, 32200, 32300, 32400, 32500, 32600, 32700, 32800, 32900, 33000, 33100, 33200, 33300, 33400, 33500, 33600, 33700, 33800, 33900, 34000, 35000, 36000, 36200, 36400, 36600, 36800, 37000, 37200, 37400, 37600, 37800, 38000, 38200, 38400, 38600, 38800, 39000, 39200, 39400, 39600, 39800, 40000, 41000, 42000, 43000, 44000, 45000, 46000, 47000, 48000, 49000, 50000, 51000, 52000, 53000, 54000, 55000
 
Note that the three lists, composed of 31, 21 and 21 frequencies, add up to one final list of 65 frequencies instead of 73. This is because duplicate frequencies are automatically removed from the final frequency list.

Underwater

The problem data and mesh units have not changed, so there is no need to modify them. However, you may want to modify the frequency intervals 2 and 3 as follows, because the resonance frequency will shift to lower due the water load.

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