*HEADING
 EC388AFAT: AC3D8 AND C3D8 ELEMENTS
 Tube with nonreflective end-condition and *TIE constraint.
 Part of the air in the tube is modelled with continuum elements
 with air properties.
************************************************
*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 5 elements are acoustic
*ELEMENT,TYPE=AC3D8
1,1,601,603,3,   201,801,803,203
*ELGEN,ELSET=ACOU
1,5,2,1
** Then 5 continuum elements
*ELEMENT,TYPE=C3D8
6,1011,1611,1613,1013,  1211,1811,1813,1213,
*ELGEN,ELSET=STRUCT
6,5,2,1
** Next 10 elements are acoustic
*ELEMENT,TYPE=AC3D8
11,21,621,623,23,221,821,823,223
*ELGEN,ELSET=ACOU
11,10,2,1
*ELSET,ELSET=NONREF
20,
************************************************
*SURFACE,TYPE=ELEMENT,NAME=ACR
5,S5
*SURFACE,TYPE=ELEMENT,NAME=SOL
6,S3
*SURFACE,TYPE=ELEMENT,NAME=SOR
10,S5
*SURFACE,TYPE=ELEMENT,NAME=ACL
11,S3
*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,
************************************************
*AMPLITUDE,NAME=OMEGA
0.,0., 1E6,6.2831853E6
************************************************
**       ** ANALYTIC SOLUTION  **
**  
**  at freq=100,
**  Impedance: Z = root( K_f rho )
**               = 415.095
**  Propagation constant 
**             b = i (omega/K_f) Z
**               = 1.8315  i
**
**  Solution: with nonreflective end,
**  Complex pressure
**             p(x) = Z v(0) exp( - b x)
**  i.e. |p(x)| = |Z v(0)| exp ( - Re(b) x)
**              =  415.095
**
**       Arg(p) = Arg(Z) - Im(b) x
**       ppor   = - 104.94 x
**
************************************************  
*Elset,Elset=ODB_ESET
ACOU, STRUCT
*Nset, Nset=ODB_NSET
ODB_NSET, NBACK, NFRONT
NALL, SAMPLE, LOAD1
************************************************  
*STEP
*STEADY STATE DYNAMIC,DIRECT
100,
**  For reference, these IMPEDANCE PROPERTY
**  constants could be used to specify the nonreflecting 
**  condition at the given frequency:
**  1/k1= 0, 1/c1= 2.40908E-03
**        0,       1/Z
**
*IMPEDANCE
 NONREF,I5
**
** Conditions at x=0 : Define the source inward accel
** to be  a =  omega i, so v (inward) = 1.
** *AMPLITUDE card enforces (2*pi)*f factor. 
** *CLOAD needs only to carry total area, distributed
** to nodes.
**
*CLOAD,LOAD CASE=2, AMP=OMEGA
LOAD1, 8, 1.5625E-04
** simulation of uniaxial condition
*BOUNDARY
NSOL,2,3
*NODE PRINT, NSET=SAMPLE
COORD,POR,PPOR
*OUTPUT,FIELD,OP=ADD,FREQUENCY=9999
*ELEMENT OUTPUT,ELSET=STRUCT
S
*NODE OUTPUT,NSET=SAMPLE
POR,
*OUTPUT,HISTORY,OP=ADD,FREQUENCY=9999
*NODE OUTPUT,NSET=SAMPLE
POR,
*ELEMENT OUTPUT,ELSET=STRUCT
COORD,S11
*END STEP