*HEADING
 EC36AFAS: AC3D6 & 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=AC3D6
 1,1,1002,2,2501,1502,2502
 2,1,1001,1002,2501,1501,1502
*ELGEN,ELSET=CHANNEL
 1,100,1,2
 2,100,1,2
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*ELEMENT,TYPE=ASI4,ELSET=LOAD
 1200,1,2501,1501,1001
*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=AC3D6
 1,1,1002,2,2501,1502,2502
 2,1,1001,1002,2501,1501,1502
*ELGEN,ELSET=CHANNEL
 1,100,1,2
 2,100,1,2
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*ELEMENT,TYPE=ASI3d3,ELSET=LOAD
 1200,1,2501,1001
 1201,2501,1501,1001
*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.199,S4
 new.199,s4
*nset,nset=channel_nodes
old.channel_nodes,new.channel_nodes
*endassembly
**************************************
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS,DEP=1
 0.999999,10
 0.1424E6,20,1
**
*RESTART,WRITE
*INITIAL CONDITIONS,TYPE=FIELD
CHANNEL_NODES,1
*INITIAL CONDITIONS,TYPE=TEMPERATURE
CHANNEL_NODES,20
**
*STEP,INC=1000
*DYNAMIC,DIRECT,APPLICATION=TRANSIENT FIDELITY
.0001,.0036
** Define nonreflective boundary at x=1
*IMPEDANCE
 old.199,I4,
 new.199,I4
**
** Prescribe  acceleration inwards of  a0=1.
**
*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,DIRECT,APPLICATION=TRANSIENT FIDELITY
.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