PAABSF

Bulk Data Entry Defines the properties of the fluid acoustic absorber element.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PAABSF PID TZREID TSIMID S A B K RHOC

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PAABSF 4 3 4 1.0 0.5

Definitions

Field Contents SI Unit Example
PID Property identification number.

(Integer > 0)
TZREID TABLEDi entry identification number that defines the resistance as a function of frequency. The real part of the impedance.

(Integer > 0 or Blank)
TZIMID TABLEDi entry identification number that defines the reactance as a function of frequency. The imaginary part of impedance.

(Integer > 0 or Blank)
S Impedance scale factor.

Default = 1.0 (Real)
A Area factor when 1 or 2 grid points are specified in the CAABSF entry.

Default = 1.0 (Real > 0.0)
B Equivalent damping coefficient.

Default = 0.0 (Real)
K Equivalent stiffness coefficient.

Default = 0.0 (Real)
RHOC Constant used in data recovery for calculating an absorption coefficient.
RHO
Media density
C
Speed of sound in the media

Default = 1.0; current unused (Real)

Comments

  1. PAABSF is referenced by a CAABSF entry only.
  2. If only one grid point is specified on the CAABSF entry, the impedance Z(f)=ZR+iZi is the total impedance at the point. If two grids are specified, then the impedance is the impedance per unit length. If three or four points are specified, then the impedance is the impedance per unit area. ZR(f)=TZREID(f)+B and Zi(f)=TZIMID(f)=K/(ω) .
  3. The resistance represents a damper quantity B. The reactance represents a quantity of the type (ωM−K/ω) . The impedance is defined as:

    Z=p/u

    Where,
    p
    Pressure
    u
    Velocity
  4. The impedance scale factor S is used in computing element stiffness and damping terms as:
    k=AS2πfZi(f)S2R+Z2i∫(of 
  5. To create a non-reflecting boundary, set the values of the TABLEDi entry referenced by the TZREID field (Resistance-real part of Impedance) to be equal to ( ( ρ f l u i d ) * ( c f l u i d ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaacq aHbpGCdaWgaaWcbaGaamOzaiaadYgacaWG1bGaamyAaiaadsgaaeqa aaGccaGLOaGaayzkaaGaaiOkamaabmaabaGaam4yamaaBaaaleaaca WGMbGaamiBaiaadwhacaWGPbGaamizaaqabaaakiaawIcacaGLPaaa aaa@4624@ for all frequencies. This will allow the acoustic wave to propagate normally through the boundary, without reflection. This condition is called the Sommerfeld boundary condition.
    Where,
    ρ f l u i d MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqyWdi3aaS baaSqaaiaadAgacaWGSbGaamyDaiaadMgacaWGKbaabeaaaaa@3C8F@
    Density of the fluid
    c f l u i d MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yamaaBa aaleaacaWGMbGaamiBaiaadwhacaWGPbGaamizaaqabaaaaa@3BB7@
    Speed of sound in the fluid
  6. This card is represented as a property in HyperMesh.