II. How To Use ATILA

7. Acoustic Lens (1)
GEOMETRY/DRAWING MATERIAL ASSIGNMENT BOUNDARY CONDITIONS MESHING


PROBLEM - Langevin Transducer 50 mm f x 40 mm t (Two PZT 8 disks with 50 mm f x 1 mm t are sandwiched by two Steel 1 blocks with 50 mm f x 19 mm thickness ) with an Rubber Acoustic Lens; 2D Axisymmetric with 1/2 portion

  • Learn how to use an acoustic lens
  • Check the Beam Patter / Directivitiy

GEOMETRY/DRAWING

Create Surface
Geometry -> Create -> Object -> Rectangle -> Enter First and Second Corner Points -> 0,0 ; 20,25
Divide Surface
Geometry -> Edit -> Divide -> Surface -> Near point -> Select Surface to Divide -> Choose NURBS sense -> VSense -> Near point 1,0

Create Lens
Geometry -> Create -> Object -> Circle -> Enter Center Point-> 0,0 -> Radius 35
Divide Surface
Geometry -> Edit -> Divide -> Surface -> Near point -> Select Surface to Divide -> Choose NURBS sense -> USense -> Near point 0,25 -> Geometry -> Delete -> Surfaces
Geometry -> Create -> Intersection -> Delete unnecessary lines and points
Geometry -> Create -> NURB Surfaces -> Automatic -> 4 sided lines

Create Water Area
Geometry -> Create -> Arc -> First, Second and Third points -> 80,0; 0,80; -80,0
Geometry -> Edit -> Divide -> Num Divisions -> Select line -> Num Divisions 2
Delete -> Line and point
Then, Geometry -> Create -> Line

MATERIAL ASSIGMENT
Piezoelectric Materials
Data -> Materials -> Piezoelectric -> PZT8 -> Assign -> Pick Surface
Elastic Materials
Data -> Materials -> Elastic -> Steel 1-> Assign -> Pick Surface
Data -> Materials -> Elastic -> Rubber -> Assign -> Pick Surface
Fluid Materials
Data -> Materials -> Fluid -> Water-> Assign -> Pick Surface
Click Draw -> All materials -> Check the material are assigned as PZT8, Steel 1 and Water

 

BOUNDARY CONDITIONS
Polarization/Local Axes

High voltage should be applied on the center surface of the PZT two layers, and Ground on the metal side surface. Choose the polarization direction along the electric field direction.

Data -> Conditions -> Surfaces -> Geometry -> Polarization (Cartesian) -> Define Polarization (P1) (1,0) direction

Choose 3PointsXZ -> Center (0,0,0) -> Define X axis by putting (0,1,0) -> Then define Z axis by putting (1,0,0) -> Escape

Assign Polarization (Local-Axes P1) -> Choose the PZT surface -> Finish

Potential

Data -> Conditions -> Lines -> Potential 0.0 (or Ground in ATILA 5.2.4 or higher version) -> Assign the right-side line of the PZT -> Forced Potential 1.0 -> Assign the left-side line of the PZT (which is the center surface of the two PZT plates)

Surface Contraints (1/2 part of the whole Cymbal)

We use only 1/2 part of the whole Langevin transducer, taking into account the symmetry; the left-side line of the PZT and water should be clamped (X component is clamped)

The bottom axisymmetric line of the whole system (including water) - Y component is clamped. The axisymmetric axis is taken along x axis (This is the rule in ATILA).

Data -> Conditions -> Lines -> Line Constraints -> X components -> Clamped -> Assign the left-side PZT and Water lines

Similarly, on the Axisymmetric X axis -> Line Contstraints -> Y & Z components -> Clamped -> Assign

Radiation Boundary

Data -> Conditions -> Lines -> Line Constraints -> X components -> Clamped -> Assign the left-side PZT and Water lines

Radiation boundary is applied not to reflect the water-propagating sound at this boundary (like an anechoic wall). In this sense, the radius of this water boundary is not essential.

To check the assignment -> Draw -> All conditions -> Include local axes

MESHING

Mapped Mesh

Meshing -> Structured -> Surfaces -> Select all Surfaces -> Then Cancel the further process
Meshing -> Structured -> Lines -> Enter number to divide line -> Choose "1, 2, 4" for the lines -> Generate

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