*HEADING
 EC34AFAS: AC3D4 and ASI4
 1D transient wave propagation in an acoustic medium with 
 prescribed acceleration on dof 1. 
 Verification problem: Transient Dynamics Tests.
**
** C = root (K/rho)= 343.05 m/s   K=bulk mod, rho=density.  
**
** Analytic solution to prescribed constant acceleration of a0 at x=0
** 
** p(x,t) = (K a0 / c^2) (ct - x)  for x < ct
**        = 0  			   for x > ct
** 
*PREPRINT,ECHO=NO,HISTORY=YES,MODEL=YES
**
*part,name=old
*NODE, Nset=ODB_NSET
    1, 0,
  101, 1,
 1001, 0, 1e-2
 1101, 1, 1e-2
 1501, 0, 1e-2, -1e-2
 1601, 1, 1e-2, -1e-2
 2501, 0, 0, -1e-2
 2601, 1, 0, -1e-2
*NGEN,NSET=CHANNEL_NODES
    1,101
 1001,1101
 1501,1601
 2501,2601
*NSET,NSET=SAMPLE,GENERATE
 1,101
*NSET,NSET=LOAD
 1,1001,1501,2501
*ELEMENT,TYPE=AC3D4
    1,    1, 1002,    2, 2501
    2, 1002,    2, 2501, 1502
    3,    2, 2501, 1502, 2502
    4,    1, 1001, 1002, 2501
    5, 1001, 1002, 2501, 1501
    6, 1002, 2501, 1501, 1502
*ELGEN,ELSET=CHANNEL
 1,100,1,6
 2,100,1,6
 3,100,1,6
 4,100,1,6
 5,100,1,6
 6,100,1,6
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
**
** note that the ASI4 elements are degenerated
** to 3 - noded geometry. "ASI3" is a quadratic
** line element.
**
*ELEMENT,TYPE=ASI4,ELSET=LOAD
 2000,1,2501,1001,1001
 2010,2501,1501,1001,2501
*INTERFACE,ELSET=LOAD
*endpart
*part,name=new
*NODE, Nset=ODB_NSET
    1, 0,
  101, 1,
 1001, 0, 1e-2
 1101, 1, 1e-2
 1501, 0, 1e-2, -1e-2
 1601, 1, 1e-2, -1e-2
 2501, 0, 0, -1e-2
 2601, 1, 0, -1e-2
*NGEN,NSET=CHANNEL_NODES
    1,101
 1001,1101
 1501,1601
 2501,2601
*NSET,NSET=SAMPLE,GENERATE
 1,101
*NSET,NSET=LOAD
 1,1001,1501,2501
*ELEMENT,TYPE=AC3D4
    1,    1, 1002,    2, 2501
    2, 1002,    2, 2501, 1502
    3,    2, 2501, 1502, 2502
    4,    1, 1001, 1002, 2501
    5, 1001, 1002, 2501, 1501
    6, 1002, 2501, 1501, 1502
*ELGEN,ELSET=CHANNEL
 1,100,1,6
 2,100,1,6
 3,100,1,6
 4,100,1,6
 5,100,1,6
 6,100,1,6
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
**
** note that the ASI3D3 elements are 3 - noded geometry.
**
*ELEMENT,TYPE=ASI3D3,ELSET=LOAD
 2000,1,2501,1001
 2010,2501,1501,1001
*INTERFACE,ELSET=LOAD
*endpart
**
*assembly,name=both
*instance,name=old,part=old
*endinstance
*instance,name=new,part=new
0,0.05,0
*endinstance
*nset,nset=sample
old.sample,new.sample
*nset,nset=load
old.load,new.load
*surface,NAME=NRS
 old.597,S4,
 old.596,S2
 new.597,S4,
 new.596,S2,
*endassembly
**************************************
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
**
**
*RESTART,WRITE
**
*STEP,INC=1000
*DYNAMIC
.0001,.0036
** Define nonreflective boundary at x=1
*IMPEDANCE
 old.597,I4,
 old.596,I2
 new.597,I4,
 new.596,I2,
**
** Prescribe volume acceleration inwards
**   of  a0=1.
** Acceleration of interface element specified.
*BOUNDARY,TYPE=ACCELERATION
 LOAD,1,1,1.
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE,FREQ=6
 POR,
*OUTPUT,FIELD, OP=NEW,Frequency=6
*NODE OUTPUT
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*ENDSTEP
***********************
*STEP,INC=1000
*DYNAMIC
.0001,.0008
*IMPEDANCE,OP=NEW
*SIMPEDANCE
 NRS,
*BOUNDARY,TYPE=ACCELERATION
 LOAD,1,1,1.
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE,FREQ=6
 POR,
*OUTPUT,FIELD, OP=NEW,Frequency=6
*NODE OUTPUT
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*ENDSTEP