*HEADING
 Tube with nonreflective end-condition and *TIE constraint.
 Part of the air in the tube is modelled with continuum elements
 with air properties.
************************************************
*preprint,model=yes,history=yes
*NODE, Nset=ODB_NSET
1, 
41,.5
101,,0.0125
141,0.5,0.0125
201,,0.025
241,0.5,0.025
*NGEN,NSET=NBACK
1,41
101,141
201,241
*NCOPY,CHANGE NUMBER=600, OLD SET=NBACK, NEW SET=NFRONT,SHIFT
0.0,0.0,0.025

*NSET,NSET=NALL
NBACK,NFRONT
*NSET,NSET=SAMPLE,GEN
1,41
*NSET,NSET=LOAD1
1,201,801,601
************************************************
*NCOPY,OLDSET=NALL,NEWSET=NSOL,CHANGENUMBER=1000,SHIFT
0.0,0.0,0.0
1.0,0.0,0.0,0.0,1.0,0.0
************************************************
** First 30 elements are acoustic
*ELEMENT,TYPE=AC3D4
 1,    1,  601,  603,  201
 2,  601,  603,  201,  801
 3,  603,  201,  801,  803
 4,  603,    3,    1,  803
 5,    3,    1,  803,  203
 6,    1,  803,  203,  201
*ELGEN,ELSET=ACOU
1,5,2,6
2,5,2,6
3,5,2,6
4,5,2,6
5,5,2,6
6,5,2,6
** Then 5 continuum elements
*ELEMENT,TYPE=C3D8R
1006,1011,1611,1613,1013,  1211,1811,1813,1213,
*ELGEN,ELSET=STRUCT
1006,5,2,1
** Next elements are acoustic
*ELEMENT,TYPE=AC3D4
101,   21,  621,  623,  221
102,  621,  623,  221,  821
103,  623,  221,  821,  823
104,  623,   23,   21,  823
105,   23,   21,  823,  223
106,   21,  823,  223,  221
*ELGEN,ELSET=ACOU
101,10,2,6
102,10,2,6
103,10,2,6
104,10,2,6
105,10,2,6
106,10,2,6
*ELSET,ELSET=NONREF
120,
************************************************
*SURFACE,TYPE=ELEMENT,NAME=ACR
28,S2
29,S4
*SURFACE,TYPE=ELEMENT,NAME=SOL
1006,S3
*SURFACE,TYPE=ELEMENT,NAME=SOR
1010,S5
*SURFACE,TYPE=ELEMENT,NAME=ACL
101,S2
102,S4
*TIE,NAME=CRAVAT
SOL,ACR
ACL,SOR
************************************************
**
**  Acoustic Element Properties
**
*SOLID SECTION,MATERIAL=AIR,ELSET=ACOU
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
************************************************
**
**  Continuum Element Properties
**
*SOLID SECTION,MATERIAL=AIRSOLID,ELSET=STRUCT
*MATERIAL,NAME=AIRSOLID
*DENSITY
 1.21,
*ELASTIC
 0.1424E6,
************************************************
*Elset,Elset=ODB_ESET
ACOU, STRUCT
*Nset, Nset=ODB_NSET
ODB_NSET, NBACK, NFRONT
NALL, SAMPLE, LOAD1
*Nset, Nset=struct_sample
1211,1811,1813,1213
************************************************ 
*STEP
*FREQUENCY
70,
*OUTPUT,FIELD,FREQ=0
*END STEP
**------------------------------------------------
*STEP,inc=10000
*MODAL DYNAMIC
0.00001,.005
*CLOAD
LOAD1, 8,314.1592654
** simulation of uniaxial condition
*OUTPUT,FIELD,FREQ=1000
*ELEMENT OUTPUT,ELSET=STRUCT
S
*NODE OUTPUT,NSET=SAMPLE
POR,
*OUTPUT,HISTORY,FREQUENCY=1
*NODE OUTPUT,NSET=SAMPLE
POR,
*NODE OUTPUT,NSET=struct_sample
u1,
*END STEP
**------------------------------------------------
*STEP,inc=10000
*DYNAMIC
0.00001,.005
*CLOAD
LOAD1, 8,314.1592654
** simulation of uniaxial condition
*OUTPUT,FIELD,FREQ=1000
*ELEMENT OUTPUT,ELSET=STRUCT
S
*NODE OUTPUT,NSET=SAMPLE
POR,
*OUTPUT,HISTORY,FREQUENCY=1
*NODE OUTPUT,NSET=SAMPLE
POR,
*NODE OUTPUT,NSET=struct_sample
u1,
*END STEP