Home / Examples / Coupled Analysis / Piezoelectric-Acoustic Analysis [Rayleigh/Mach] / Example 2: Fully Coupled Analysis

Example 2: Fully-Coupled Analysis

General

Fully-coupled analysis is performed for the example 1: Harmonic Analysis.

Results will vary depending on Femtet version and the PC environment.

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	m

Analysis Conditions

The solvers are Rayleigh and Mach.

Item	Settings
Solver	Piezoelectric Analysis [Rayleigh] Acoustic Analysis [Mach]
Analysis Type	Harmonic Analysis
Options	Select [Fully-coupled Analysis]

The harmonics analysis tab is set up as follows.

The sound waves propagate outside the analysis region. Therefore the open boundary condition below is applied initially.

The default conditions will be applied.

Tabs	Setting Item	Settings
Harmonic Analysis	Frequency	Minimum: 1500 [Hz] Maximum: 1700 [Hz]
Harmonic Analysis	Sweep Type: Linear Step by Division Number	Division: 10
Open Boundary Tab	Type	Absorbing Boundary
	Order of Absorbing Boundary	1st-order
	Coordinates of Origin	x = y = z = 0

Model

A piezoelectric disc (Unit) is placed on an aluminum disc (Plate). The hemispheric body (Air) covers the upper area.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	Air	000_Air(*)
1/Solid	Unit	000_P-4 *
2/Solid	Plate	001_Al *

* Available from the material DB

Unit and Plate are for the piezoelectric analysis only, whereas Air is for the acoustic analysis only.

Body Attribute Name	Analysis Domain (Solver)
Unit	Piezoelectric Analysis (Rayleigh)
Plate	Piezoelectric Analysis (Rayleigh)
Air	Acoustic Analysis (Mach)

Cautions:

In this analysis, it is necessary to specify the analysis domain.

That is to specify either piezoelectric analysis or acoustic analysis on the analysis domain tab.

Boundary Conditions

The side periphery of the model is fixed in the Z direction.

Electric wall is set on the top and bottom faces of the piezoelectric disc.

The open boundary is set on the hemispheric surface.

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
V0/Face	Electric	Electric Wall	Electric Potential Specified: Electric Potential 0 [V]
V1/Face	Electric	Electric Wall	Electric Potential Specified: Electric Potential 10 [V]
Fix/Face	Mechanical	Displacement	Select UZ and set UZ=0
Open	Acoustic	Open Boundary

Results

The displacement of the piezoelectric disc is examined.

Horizontal axis: Frequency, Vertical axis: Displacement Z component. The displacement is measured at the center (0, 0, 0) of the disc where the magnitude of displacement is the largest.

Under the fully coupled condition, the air can suppress the vibration of the disc, so the displacement magnitude is smaller at the resonant frequency of 1.6 [kHz]. When moving away from the resonant frequency, the difference in magnitude becomes very small.