5.1. Basic Material Parameters of Acoustic Media

Several primary commands are available to define basic acoustic material properties:

TB,AFDM,,,,MAT

TBFIELD

TBDATA,1,DENS,SONC,VISC,KXX,CPH,CVH

TBDATA,7,BVIS,DELTA,BETA

Acoustic analyses require the mass density (MP,DENS) and sound speed (MP,SONC) of the acoustic fluid.

For viscous-thermal material, the dynamic viscosity (MP,VISC), bulk viscosity (MP,BVIS), thermal conductivity (MP,KXX), heat coefficient at constant volume (MP,CVH), and heat coefficient at constant pressure (MP,C) are defined.

For nonlinear acoustics, the diffusivity of sound (DELTA in TB,AFDM,,,,MAT or MP,SDIF) and the dimensionless nonlinearity coefficient (BETA in TB,AFDM,,,,MAT or or MP,BETW) are defined. Alternatively, the program calculates the diffusivity of sound from defined dynamic viscosity, bulk viscosity, thermal conductivity, heat coefficient at constant volume, and heat coefficient at constant pressure.

Example 5.1: Defining Acoustic Material Properties (MP)

The following example input defines the acoustic material properties of air via the MP command:

mp,dens,1,1.21     ! mass density
mp,sonc,1,343      ! sound speed
mp,visc,1,1.827e-5 ! dynamic viscosity
mp,bvis,1,1.096e-5 ! bulk viscosity
mp,kxx,1,0.0257    ! thermal conductivity
mp,cvh,1,718       ! heat coefficient at a constant volume per mass
mp,c,1,1005        ! heat coefficient at a constant pressure per mass
mp,betw,1,1.2      ! nonlinearity coefficient
mp,sdif,1,3.764e-5 ! diffusivity of sound

Frequency-dependent material properties are defined via the TB,AFDM,,,,MAT command. Material values defined by TB,AFDM override the values defined by MP.

Frequency-dependent material properties are interpolated if the working frequency is not one of the frequencies defined via the TBFIELD command.

Example 5.2: Defining Frequency-Dependent Acoustic Material Properties (TB)

The following example input defines frequency-dependent acoustic material properties via the TB command:

tb,afdm,1,,,mat                             ! basic acoustic materials
tbfield,freq,f1                             ! table at frequency f1
tbdata,1,dens1,sonc1,visc1,therm1,cph1,cvh1 ! material parameters table
tbdata,7,bvis1
tbfield,freq,f2                             ! table frequency f2 
tbdata,1,dens2,sonc2,visc2,therm2,cph2,cvh2 ! material parameters table
tbdata,7,bvis2

Listing the Defined Material Properties

The MPLIST command lists the material properties defined via the MP command.

The TBLIST command lists the frequency-dependent material properties defined via the TB command.