Resonance in Cavityexamples|products|Murata Software Co., Ltd.

Example5 Resonance in Cavity

General

 

  • The resonance of sound waves excited in a cavity is analyzed.
     

  • The sound waves radiated from the cavity are peaked when the excitation frequency matches the cavity’s resonant frequency.
     

  • Unless specified in the list below, the default conditions will be applied.
     

 

Analysis Space

Item

Settings

Analysis Space

Axisymmetric

Model unit

mm

 

Analysis Conditions

Item

Settings

Solver

Acoustic Analysis [Mach]

Analysis Type

Harmonic analysis

Options

N/A

 

The tab setting is listed below.

Tabs

Setting Item

Settings

 

Frequency

Minimum: 1,000[Hz]

Maximum: 10,000[Hz]

Harmonic analysis

Sweep Type

Division number: 190

 

Sweep Setting

Select Fast sweep.

 

 

 

Open boundary

Coordinates of Origin

x = 0

z = 0

Model

It is axisymmetric, so just right half of the section is created with a sheet body and defined as air. The open boundary is set on the perimeter of the quadrant circle representing the surface of the cavity.

The speed is set as the boundary condition on the bottom of the cavity.

 

 

 

Body Attributes and Materials

Body Number/Type

Body Attribute Name

Material Name

8/Sheet

AIR

000_Air(*)

* Available from the Material DB

 

 

Boundary Conditions

The “speed” boundary condition is set on the bottom and the “open boundary” condition is set on the perimeter.

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Settings

v/Edge

Acoustic

Speed

1[m/s]

Open/Face

Acoustic

Open boundary

 

 

 

Results

The Figure below is the frequency plot of the sound pressure level [dB] at x=0, Z=10.

It is peaked at 8.9[kHz].

 

 

It is very close to 8.46[kHz], the result calculated from the Helmholtz resonance equation below.

 

C: Sound speed, V: Volume of cavity

 

 

 

The gradation contour of the sound pressure level at 8.6[Hz] is shown below.

 

 

 

The sound pressure is quite high in the cavity.