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II.
How To Use ATILA
6.3
Tonpilz Sonar (1)
GEOMETRY/DRAWING MATERIAL
ASSIGNMENT
PROBLEM
- Tonpilz Transducer under Water, Axisymmetry, PZT8, Steel
and Aluminum

This part describes the harmonic (frequency domain) analysis
of a Tonpilz-type transducer. First, the transducer is considered
without loading (in-vacuum); then, it is considered to be radiating
in water. The transducer is assumed to be axisymmetrical, thus
the model is two-dimensional and only a cross-section of the transducer
is represented.
GEOMETRY/DRAWING
The dimensions used for the geometry are (in
mm) shown in the next table, along with the material type.
Ceramic Rings |
Inner Radius |
6 |
PZT8 |
Outer Radius |
18 |
Prestress Rod |
Length |
64 |
Steel |
Small Radius |
4 |
Large Radius |
6 |
Headmass |
Inner Radius |
6 |
Aluminum |
Small Outer Radius |
18 |
Large Outer Radius |
20 |
Tailmass |
Inner Radius |
6 |
Steel |
Small Outer Radius |
20 |
Large Outer Radius |
23 |
Nut |
Inner Radius |
6 |
Steel |
Outer Radius |
10 |
Water |
Radius |
56 |
Water |
Because this is an axisymmetrical problem, many
quantities are affected by a 2π factor of symmetry, such
as the impedance, for instance. Always make
sure to verify that the factor of symmetry is properly taken
into account. Generally speaking, all results in the ATILA-GiD
interface are provided without correction for the factor of symmetry.
The coordinates of the points you will need
to create are shown in the table below, for reference. It is
better for acoustic radiation
problems to position the origin of the acoustic source (center
of the piston face) at the origin of the global coordinate system.
Although, we do not consider the acoustic radiation problem in
the first part of this tutorial, it will save time later to follow
the same rules. For this reason, the solid part of the transducer
is located in the negative X region, and the fluid domain is
in the positive X region.
Note that because ATILA
uses the X axis as the axis of axisymmetry, the points are
all in the positive Y region of the plane. The
coordinates of the points
you need to create are arranged in the following table.
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(-39,23) |
(-33,23) |
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(-55,20) |
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(-39,20) |
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(-8,20) |
(0,20) |
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(-33,18) |
(-23,18) |
(-13,18) |
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(-64,10) |
(-55,10) |
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(-64,6) |
(-55,6) |
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(-33,6) |
(-23,6) |
(-13,6) |
(-8,6) |
(0,6) |
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(-50,4) |
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(-13,4) |
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(-64,0) |
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(0,0) |
Remember that there is more than one way to enter points in GiD in Cartesian
and polar coordi-nates. Please refer to the online help in GiD for further
details. Use GiD functions to create points, lines, and surfaces until you
obtain the same result as that shown in the next figure.
MATERIAL
ASSIGMENT
Piezoelectric Materials
Assign material PZT8 to the two ceramic surfaces. Note that the definition
of the material PZT8 includes losses. You can verify the loss angles
by
clicking on the Losses tab. The values Delta_m, Delta_p,
and Delta_d correspond to the loss angle for the mechanical, piezoelectric
and dielectric tensors, respectively.
Elastic Materials 
Assign material STEEL1 to the Tailmass, Prestress
Rod, and Nut surfaces, then material ALUMINUM1 to the Headmass surface.
Assign material STEEL1 to the Tailmass, Prestress Rod,
and Nut surfaces, then material ALUMINUM1 to the Headmass surface.
When this is done, the material assignment should be similar to the following
image (you can obtain this by selecting, on any material window, the option Draw
| All materials).
Surrounding Medium 
Add the required points, lines, and surfaces, to create
the water domain. The water domain has a radius of
56mm. Because the geometry
of the transducer was created such that the center of the piston would be
at the origin of the global coordinate system, the water domain is also centered
at the origin. If needed, look in the GiD documentation about how to create
an arc.
Open the Fluid materials window and assign Water to
the water domain. Verify the material assignment with Draw | All materials.
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