Following are the boundary conditions and loading applied to the piezoelectric flextensional transducer model:
Because a quarter of the model is analyzed, two symmetry boundary conditions are applied along the x and y axes. The 3D model has an additional z constraint on both planes at z = 0 and 0.01 m.
The naturally occurring boundary condition is a rigid wall or a symmetry plane, so no acoustic boundary conditions are necessary on the two symmetry planes at x = 0 and y = 0. In the 3D case, the planar surfaces at z = 0 and 0.01 m are rigid walls.
To active the vibroacoustic coupling, the FSI flag is specified to the nodal component N_FSI .
For the 2D case, FLUID129 infinite acoustic element is used to model the wave-absorption condition. Typically, the fluid domain can be truncated around a quarter of the wavelength away from the object of interest. Because far-field postprocessing is not supported for 2D FLUID29 elements, however, the calculated results at 1 m must be included in the computational domain. FLUID129 elements are therefore positioned in a circular arc 1.1 m from the center.
For the 3D case, the modeled domain is Cartesian. A Robin radiation flag (SF,,INF) is applied to the outermost (+x and +y) surfaces to model the wave-absorption condition. Because far-field postprocessing is supported in 3D, it is not necessary for the computational domain to extend 1 m in distance.