*HEADING
 1D transient wave propagation,structure- acoustic coupling (between AC3D8 and C3D8 elements), 
 incident wave load, spherical and defined through pressure amplitude
**
** C = root (K/rho)= 343.05 m/s   (in acoustic medium)  
**
** C = root (K/rho)=  31.62 m/s   (in solid medium) K=bulk mod, rho=density.
**
*PREPRINT,ECHO=NO,HISTORY=NO,MODEL=YES
*NODE, NSET=ACOUSTIC
 1, 0, 0, 0
 2, 1, 0, 0
 3, 1, 1, 0
 4, 0, 1, 0
 5, 0, 0, 1
 6, 1, 0, 1
 7, 1, 1, 1
 8, 0, 1, 1
*NODE,NSET=SOLID
 1001, 1, 0, 0
 1002, 2, 0, 0
 1003, 2, 1, 0
 1004, 1, 1, 0
 1005, 1, 0, 1
 1006, 2, 0, 1
 1007, 2, 1, 1
 1008, 1, 1, 1
*ELEMENT,TYPE=AC3D8,ELSET=ACOUSTIC
 1, 1,2,3,4,5,6,7,8
*ELEMENT,TYPE=C3D8,ELSET=SOLID
 1001, 1001,1002,1003,1004,1005,1006,1007,1008
**************************
*SURFACE,NAME=IW_LOAD_ACOUSTIC
1,S4
*SURFACE,NAME=IW_LOAD_SOLID
1001,S6
*SURFACE,NAME=TIE_ACOUSTIC
1,S4
*SURFACE,NAME=TIE_SOLID
1001,S6
**************************
*SOLID SECTION,MATERIAL=AIR,ELSET=ACOUSTIC
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
**
*SOLID SECTION,MATERIAL=SOLID,ELSET=SOLID
 1.E-4, 
**
*MATERIAL,NAME=SOLID
*DENSITY
 1.E3,
*ELASTIC
 1.E6,0.0
**
**************************
*INCIDENT WAVE PROPERTY,NAME=IWPROP,TYPE=SPHERE
0.0,0.0,
-10.0E04,0.0,
*INCIDENT WAVE FLUID PROPERTY
0.1424E6,1.21,0.0
*AMPLITUDE,DEFINITION=TABULAR,NAME=PRESSUREVTIME_ACOUSTIC
0.0,0.0,1.0,-1.0
*AMPLITUDE,DEFINITION=TABULAR,NAME=PRESSUREVTIME_SOLID
0.0,0.0,1.0,-1.0
**************************
**
*BOUNDARY
SOLID,2,2
1002,1,1
1003,1,1
1006,1,1
1007,1,1
**************************
**
*TIE,NAME=COUPLING
TIE_ACOUSTIC,TIE_SOLID
**************************
*RESTART,WRITE
**
*STEP,INC=1000
*DYNAMIC,ALPHA=0.0
.0001,.005
**
*INCIDENT WAVE,PRESSUREAMPLITUDE=PRESSUREVTIME_ACOUSTIC,PROPERTY=IWPROP
IW_LOAD_ACOUSTIC,415.09517
*INCIDENT WAVE,PRESSUREAMPLITUDE=PRESSUREVTIME_SOLID,PROPERTY=IWPROP
IW_LOAD_SOLID,415.09517
**
*NODE PRINT,NSET=ACOUSTIC,FREQ=20
 POR,
*NODE PRINT,NSET=SOLID,FREQ=20
 U,
*OUTPUT,FIELD,VAR=PRESELECT,FREQ=1
*OUTPUT,FIELD,FREQ=1
*NODE OUTPUT,NSET=ACOUSTIC
 POR,
*NODE OUTPUT,NSET=SOLID
 U,
*ELEMENT OUTPUT,ELSET=SOLID
 S,
*OUTPUT,HISTORY,FREQ=1
*NODE OUTPUT,NSET=ACOUSTIC
 POR,
*NODE OUTPUT,NSET=SOLID
 U,
*ELEMENT OUTPUT,ELSET=SOLID
 S,
*ENDSTEP