II. How To Use ATILA

6.3 Tonpilz Sonar (3)
MESHING


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


MESHING

ATILA requires that the mesh be composed exclusively of second order elements. The corre-sponding setting can be found under the Meshing menu. Select Quadratic Elements, then Quadratic. Note that this option is automatically set when you open the ATILA-GiD interface.

We will create mix of structured rectangles mesh and unstructured triangle mesh. Note that such mixing of element types in GiD is currently only available in 2D. Also note that only four-sided surfaces can be structured.
First, we define the structured mesh. Select Meshing | Structured | Surfaces.

Apply this meshing condition to the piezoelectric surfaces.

GiD then requests further information about the number of subdivisions that should be applied to lines (this will structure the mesh). Select 6 mesh subdivisions and apply to all the lines.

Because the remainder of the geometry is meshed automatically, proceed by selecting Meshing | Generate. Apply a default size value of 1.9 for the automatic mesh (in the same units as the rest of the model).

 

When GiD has terminated the mesh generation, a window is displayed with information about the number of elements that were generated. The mesh is shown in the next figure.

Note that the mesh depends on your settings. To access the settings, select Preferences from the Utilities menu, then open the Meshing tab. The settings used to produce the mesh of this tutorial are shown below.

Note that we desire to produce a fine mesh here, because it will be desired to compute stresses in the transducer. Stresses are obtained as first derivative of the finite element problem unknowns (displacements). For these derivatives to be evaluated correctly, a dense mesh is required.

MESHING (Water)

The mesh can be immediately generated. Previous definitions of the structured mesh are still pre-sent in the model. The new water domain will be meshed automatically. The mesh below was obtained with a default element size set to 1.9.