*HEADING
Acoustic test - 1D Problem, Transient; A 4m long tube; from left to right,
a sound source, 3m is air, then 1m of a highly absorbent material, followed 
by a rigid termination. [AC2D4R]
**
** See ch. 3.7.1 of ABAQUS/Verification Manual
**
*PREPRINT,ECHO=NO,HISTORY=NO,MODEL=NO
*******************************
**To test different frequencies change the value here
*Parameter
f=100.0
T=1.0/f
omega=2*3.14159*f
*******************************
**
**
**
**   Mesh Generation
**
*NODE, Nset=ODB_NSET
    1,0,
  401,4,
 1001,0, 2E-2
 1401,4, 2E-2
*NGEN,NSET=ALL
   1,401
 1001,1401
*NSET,NSET=SAMPLE,GENERATE
 1,401
*NSET,NSET=LOAD
 1,1001
*ELEMENT,TYPE=AC2D4R
 1,1,2,1002,1001
*ELGEN,ELSET=CHANNEL
 1,300
*ELEMENT,TYPE=AC2D4R
  301,301,302,1302,1301
*ELGEN,ELSET=ABSORB
  301,100
*NSET, NSET=INTERFACE
1301,1300,300,601, 301,302,1302,
*NSET, NSET=ODB_NSET
ODB_NSET, INTERFACE
**
**
************************************************
**    ** ELEMENT PROPERTIES **
**
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*SOLID SECTION,MATERIAL=ABSORB,ELSET=ABSORB
**
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
**
**
*MATERIAL,NAME=ABSORB
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
*ACOUSTIC MEDIUM,VOLUMETRIC DRAG
 1e4,
**
*AMPLITUDE,NAME=SINE,DEF=PERIODIC
1,<omega>,0.0,0.0
-1.0,0,0,0
*STEP
*DYNAMIC,EXPLICIT
,<T>
**
** Prescribe outward acceleration of 100 at loaded nodes.
** The tributary area of each node is 1/100, so the
** outward volume acceleration is 1.
**
*CLOAD,AMP=SINE
LOAD,8,-1.0
**
*OUTPUT,FIELD,NUM=1
*NODE OUTPUT
POR,
*OUTPUT,HISTORY,FREQ=10
*NODE OUTPUT,NSET=ODB_NSET
 POR,
*ENDSTEP